diff --git a/package.json b/package.json
index 4d67cb8..1e70db2 100644
--- a/package.json
+++ b/package.json
@@ -17,6 +17,7 @@
   },
   "dependencies": {
     "@types/fs-extra": "^8.0.0",
+    "chokidar": "^3.3.0",
     "colorette": "^1.1.0",
     "fs-extra": "^8.1.0",
     "globby": "10.0.1",
diff --git a/src/index.js b/src/index.js
index e0deeaf..b23f4bc 100644
--- a/src/index.js
+++ b/src/index.js
@@ -5,6 +5,7 @@ import fs from 'fs-extra'
 import isObject from 'is-plain-object'
 import globby from 'globby'
 import { bold, green, yellow } from 'colorette'
+import chokidar from 'chokidar'
 
 function stringify(value) {
   return util.inspect(value, { breakLength: Infinity })
@@ -27,6 +28,63 @@ function generateCopyTarget(src, dest, rename) {
   }
 }
 
+function generateCopyTargets(src, dest, rename) {
+  return Array.isArray(dest)
+    ? dest.map(destination => generateCopyTarget(src, destination, rename))
+    : [generateCopyTarget(src, dest, rename)]
+}
+
+async function copyFiles(copyTargets, verbose, copyOptions) {
+  if (Array.isArray(copyTargets) && copyTargets.length) {
+    if (verbose) {
+      console.log(green('copied:'))
+    }
+
+    for (const { src, dest } of copyTargets) {
+      await fs.copy(src, dest, copyOptions)
+
+      if (verbose) {
+        console.log(green(`  ${bold(src)} → ${bold(dest)}`))
+      }
+    }
+  } else if (verbose) {
+    console.log(yellow('no items to copy'))
+  }
+}
+
+function watchFiles(targets, verbose, copyOptions) {
+  return targets.map(({ src, dest, rename }) => {
+    async function onChange(matchedPath) {
+      const copyTargets = generateCopyTargets(matchedPath, dest, rename)
+      await copyFiles(copyTargets, verbose, copyOptions)
+    }
+
+    return chokidar.watch(src, { ignoreInitial: true })
+      .on('change', onChange)
+      .on('add', onChange)
+  })
+}
+
+function verifyTargets(targets) {
+  if (Array.isArray(targets) && targets.length) {
+    for (const target of targets) {
+      if (!isObject(target)) {
+        throw new Error(`${stringify(target)} target must be an object`)
+      }
+
+      const { src, dest, rename } = target
+
+      if (!src || !dest) {
+        throw new Error(`${stringify(target)} target must have "src" and "dest" properties`)
+      }
+
+      if (rename && typeof rename !== 'string' && typeof rename !== 'function') {
+        throw new Error(`${stringify(target)} target's "rename" property must be a string or a function`)
+      }
+    }
+  }
+}
+
 export default function copy(options = {}) {
   const {
     copyOnce = false,
@@ -37,6 +95,9 @@ export default function copy(options = {}) {
   } = options
 
   let copied = false
+  let watchers = []
+
+  verifyTargets(targets)
 
   return {
     name: 'copy',
@@ -49,20 +110,8 @@ export default function copy(options = {}) {
 
       if (Array.isArray(targets) && targets.length) {
         for (const target of targets) {
-          if (!isObject(target)) {
-            throw new Error(`${stringify(target)} target must be an object`)
-          }
-
           const { src, dest, rename, ...restTargetOptions } = target
 
-          if (!src || !dest) {
-            throw new Error(`${stringify(target)} target must have "src" and "dest" properties`)
-          }
-
-          if (rename && typeof rename !== 'string' && typeof rename !== 'function') {
-            throw new Error(`${stringify(target)} target's "rename" property must be a string or a function`)
-          }
-
           const matchedPaths = await globby(src, {
             expandDirectories: false,
             onlyFiles: false,
@@ -72,33 +121,22 @@ export default function copy(options = {}) {
 
           if (matchedPaths.length) {
             matchedPaths.forEach((matchedPath) => {
-              const generatedCopyTargets = Array.isArray(dest)
-                ? dest.map(destination => generateCopyTarget(matchedPath, destination, rename))
-                : [generateCopyTarget(matchedPath, dest, rename)]
-
-              copyTargets.push(...generatedCopyTargets)
+              copyTargets.push(...generateCopyTargets(matchedPath, dest, rename))
             })
           }
         }
       }
 
-      if (copyTargets.length) {
-        if (verbose) {
-          console.log(green('copied:'))
-        }
-
-        for (const { src, dest } of copyTargets) {
-          await fs.copy(src, dest, restPluginOptions)
+      await copyFiles(copyTargets, verbose, restPluginOptions)
 
-          if (verbose) {
-            console.log(green(`  ${bold(src)} → ${bold(dest)}`))
-          }
-        }
-      } else if (verbose) {
-        console.log(yellow('no items to copy'))
+      if (!copied && !copyOnce && process.env.ROLLUP_WATCH === 'true') {
+        watchers = watchFiles(targets, verbose, restPluginOptions)
       }
 
       copied = true
+    },
+    _closeWatchers: async () => { // For unit tests
+      await Promise.all(watchers.map(watcher => watcher.close()))
     }
   }
 }
diff --git a/tests/index.test.js b/tests/index.test.js
index b5f08df..1a3a592 100644
--- a/tests/index.test.js
+++ b/tests/index.test.js
@@ -2,6 +2,7 @@ import { rollup, watch } from 'rollup'
 import fs from 'fs-extra'
 import replace from 'replace-in-file'
 import { bold, yellow, green } from 'colorette'
+import { join } from 'path'
 import copy from '../src'
 
 process.chdir(`${__dirname}/fixtures`)
@@ -16,12 +17,14 @@ afterEach(async () => {
 })
 
 async function build(options) {
+  const copyPlugin = copy(options)
   await rollup({
     input: 'src/index.js',
     plugins: [
-      copy(options)
+      copyPlugin
     ]
   })
+  return copyPlugin
 }
 
 describe('Copy', () => {
@@ -230,6 +233,137 @@ describe('Copy', () => {
   })
 })
 
+describe('Watching', () => {
+  test('Does not watch target files when watch mode disabled', async () => {
+    await build({
+      targets: [
+        { src: 'src/assets/asset-1.js', dest: 'dist' }
+      ]
+    })
+
+    expect(await fs.pathExists('dist/asset-1.js')).toBe(true)
+    await fs.remove('dist')
+    expect(await fs.pathExists('dist/asset-1.js')).toBe(false)
+
+    await replace({
+      files: 'src/assets/asset-1.js',
+      from: 'asset1',
+      to: 'assetX'
+    })
+
+    await sleep(1000)
+
+    expect(await fs.pathExists('dist/asset-1.js')).toBe(false)
+
+    await replace({
+      files: 'src/assets/asset-1.js',
+      from: 'assetX',
+      to: 'asset1'
+    })
+  })
+
+  test('Does not watch target files when watch mode and copyOnce enabled', async () => {
+    process.env.ROLLUP_WATCH = 'true'
+    await build({
+      targets: [
+        { src: 'src/assets/asset-1.js', dest: 'dist' }
+      ],
+      copyOnce: true
+    })
+    delete process.env.ROLLUP_WATCH
+
+    expect(await fs.pathExists('dist/asset-1.js')).toBe(true)
+    await fs.remove('dist')
+    expect(await fs.pathExists('dist/asset-1.js')).toBe(false)
+
+    await replace({
+      files: 'src/assets/asset-1.js',
+      from: 'asset1',
+      to: 'assetX'
+    })
+
+    await sleep(1000)
+
+    expect(await fs.pathExists('dist/asset-1.js')).toBe(false)
+
+    await replace({
+      files: 'src/assets/asset-1.js',
+      from: 'assetX',
+      to: 'asset1'
+    })
+  })
+
+  test('Watches target files when watch mode enabled', async () => {
+    process.env.ROLLUP_WATCH = 'true'
+    const copyPlugin = await build({
+      targets: [
+        { src: 'src/assets/asset-1.js', dest: 'dist' }
+      ]
+    })
+    delete process.env.ROLLUP_WATCH
+
+    expect(await fs.pathExists('dist/asset-1.js')).toBe(true)
+    await fs.remove('dist')
+    expect(await fs.pathExists('dist/asset-1.js')).toBe(false)
+
+    await replace({
+      files: 'src/assets/asset-1.js',
+      from: 'asset1',
+      to: 'assetX'
+    })
+
+    await sleep(1000)
+
+    expect(await fs.pathExists('dist/asset-1.js')).toBe(true)
+
+    // eslint-disable-next-line no-underscore-dangle
+    await copyPlugin._closeWatchers()
+
+    await replace({
+      files: 'src/assets/asset-1.js',
+      from: 'assetX',
+      to: 'asset1'
+    })
+  })
+
+  test('Watches and copies multiple targets from same file', async () => {
+    process.env.ROLLUP_WATCH = 'true'
+    const copyPlugin = await build({
+      targets: [
+        { src: 'src/assets/asset-1.js', dest: 'dist' },
+        { src: 'src/assets/asset-1.js', dest: 'dist/2' }
+      ]
+    })
+    delete process.env.ROLLUP_WATCH
+
+    expect(await fs.pathExists('dist/asset-1.js')).toBe(true)
+    expect(await fs.pathExists('dist/2/asset-1.js')).toBe(true)
+    await fs.remove('dist')
+    expect(await fs.pathExists('dist/asset-1.js')).toBe(false)
+    expect(await fs.pathExists('dist/2/asset-1.js')).toBe(false)
+
+    await replace({
+      files: 'src/assets/asset-1.js',
+      from: 'asset1',
+      to: 'assetX'
+    })
+
+    await sleep(1000)
+
+    expect(await fs.pathExists('dist/asset-1.js')).toBe(true)
+    expect(await fs.pathExists('dist/2/asset-1.js')).toBe(true)
+
+    // eslint-disable-next-line no-underscore-dangle
+    await copyPlugin._closeWatchers()
+
+    await replace({
+      files: 'src/assets/asset-1.js',
+      from: 'assetX',
+      to: 'asset1'
+    })
+  })
+})
+
 describe('Options', () => {
   /* eslint-disable no-console */
   test('Verbose', async () => {
@@ -251,16 +385,16 @@ describe('Options', () => {
     expect(console.log).toHaveBeenCalledTimes(5)
     expect(console.log).toHaveBeenCalledWith(green('copied:'))
     expect(console.log).toHaveBeenCalledWith(
-      green(`  ${bold('src/assets/asset-1.js')} → ${bold('dist/asset-1.js')}`)
+      green(`  ${bold('src/assets/asset-1.js')} → ${bold(join('dist', 'asset-1.js'))}`)
     )
     expect(console.log).toHaveBeenCalledWith(
-      green(`  ${bold('src/assets/css/css-1.css')} → ${bold('dist/css-1.css')}`)
+      green(`  ${bold('src/assets/css/css-1.css')} → ${bold(join('dist', 'css-1.css'))}`)
     )
     expect(console.log).toHaveBeenCalledWith(
-      green(`  ${bold('src/assets/css/css-2.css')} → ${bold('dist/css-2.css')}`)
+      green(`  ${bold('src/assets/css/css-2.css')} → ${bold(join('dist', 'css-2.css'))}`)
     )
     expect(console.log).toHaveBeenCalledWith(
-      green(`  ${bold('src/assets/scss')} → ${bold('dist/scss')}`)
+      green(`  ${bold('src/assets/scss')} → ${bold(join('dist', 'scss'))}`)
     )
   })
 
diff --git a/yarn.lock b/yarn.lock
index 89fd7bf..7ca447c 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1002,6 +1002,14 @@ anymatch@^2.0.0:
     micromatch "^3.1.4"
     normalize-path "^2.1.1"
 
+anymatch@~3.1.1:
+  version "3.1.1"
+  resolved "https://registry.yarnpkg.com/anymatch/-/anymatch-3.1.1.tgz#c55ecf02185e2469259399310c173ce31233b142"
+  integrity sha512-mM8522psRCqzV+6LhomX5wgp25YVibjh8Wj23I5RPkPppSVSjyKD2A2mBJmWGa+KN7f2D6LNh9jkBCeyLktzjg==
+  dependencies:
+    normalize-path "^3.0.0"
+    picomatch "^2.0.4"
+
 aproba@^1.0.3:
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/aproba/-/aproba-1.2.0.tgz#6802e6264efd18c790a1b0d517f0f2627bf2c94a"
@@ -1182,6 +1190,11 @@ bcrypt-pbkdf@^1.0.0:
   dependencies:
     tweetnacl "^0.14.3"
 
+binary-extensions@^2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/binary-extensions/-/binary-extensions-2.0.0.tgz#23c0df14f6a88077f5f986c0d167ec03c3d5537c"
+  integrity sha512-Phlt0plgpIIBOGTT/ehfFnbNlfsDEiqmzE2KRXoX1bLIlir4X/MR+zSyBEkL05ffWgnRSf/DXv+WrUAVr93/ow==
+
 brace-expansion@^1.1.7:
   version "1.1.11"
   resolved "https://registry.yarnpkg.com/brace-expansion/-/brace-expansion-1.1.11.tgz#3c7fcbf529d87226f3d2f52b966ff5271eb441dd"
@@ -1206,7 +1219,7 @@ braces@^2.3.1:
     split-string "^3.0.2"
     to-regex "^3.0.1"
 
-braces@^3.0.1:
+braces@^3.0.1, braces@~3.0.2:
   version "3.0.2"
   resolved "https://registry.yarnpkg.com/braces/-/braces-3.0.2.tgz#3454e1a462ee8d599e236df336cd9ea4f8afe107"
   integrity sha512-b8um+L1RzM3WDSzvhm6gIz1yfTbBt6YTlcEKAvsmqCZZFw46z626lVj9j1yEPW33H5H+lBQpZMP1k8l+78Ha0A==
@@ -1309,6 +1322,21 @@ chardet@^0.7.0:
   resolved "https://registry.yarnpkg.com/chardet/-/chardet-0.7.0.tgz#90094849f0937f2eedc2425d0d28a9e5f0cbad9e"
   integrity sha512-mT8iDcrh03qDGRRmoA2hmBJnxpllMR+0/0qlzjqZES6NdiWDcZkCNAk4rPFZ9Q85r27unkiNNg8ZOiwZXBHwcA==
 
+chokidar@^3.3.0:
+  version "3.3.0"
+  resolved "https://registry.yarnpkg.com/chokidar/-/chokidar-3.3.0.tgz#12c0714668c55800f659e262d4962a97faf554a6"
+  integrity sha512-dGmKLDdT3Gdl7fBUe8XK+gAtGmzy5Fn0XkkWQuYxGIgWVPPse2CxFA5mtrlD0TOHaHjEUqkWNyP1XdHoJES/4A==
+  dependencies:
+    anymatch "~3.1.1"
+    braces "~3.0.2"
+    glob-parent "~5.1.0"
+    is-binary-path "~2.1.0"
+    is-glob "~4.0.1"
+    normalize-path "~3.0.0"
+    readdirp "~3.2.0"
+  optionalDependencies:
+    fsevents "~2.1.1"
+
 chownr@^1.1.1:
   version "1.1.2"
   resolved "https://registry.yarnpkg.com/chownr/-/chownr-1.1.2.tgz#a18f1e0b269c8a6a5d3c86eb298beb14c3dd7bf6"
@@ -2126,6 +2154,11 @@ fsevents@^1.2.7:
     nan "^2.12.1"
     node-pre-gyp "^0.12.0"
 
+fsevents@~2.1.1:
+  version "2.1.1"
+  resolved "https://registry.yarnpkg.com/fsevents/-/fsevents-2.1.1.tgz#74c64e21df71721845d0c44fe54b7f56b82995a9"
+  integrity sha512-4FRPXWETxtigtJW/gxzEDsX1LVbPAM93VleB83kZB+ellqbHMkyt2aJfuzNLRvFPnGi6bcE5SvfxgbXPeKteJw==
+
 function-bind@^1.1.1:
   version "1.1.1"
   resolved "https://registry.yarnpkg.com/function-bind/-/function-bind-1.1.1.tgz#a56899d3ea3c9bab874bb9773b7c5ede92f4895d"
@@ -2186,6 +2219,13 @@ glob-parent@^5.0.0:
   dependencies:
     is-glob "^4.0.1"
 
+glob-parent@~5.1.0:
+  version "5.1.0"
+  resolved "https://registry.yarnpkg.com/glob-parent/-/glob-parent-5.1.0.tgz#5f4c1d1e748d30cd73ad2944b3577a81b081e8c2"
+  integrity sha512-qjtRgnIVmOfnKUE3NJAQEdk+lKrxfw8t5ke7SXtfMTHcjsBfOfWXCQfdb30zfDoZQ2IRSIiidmjtbHZPZ++Ihw==
+  dependencies:
+    is-glob "^4.0.1"
+
 glob@^7.1.1, glob@^7.1.2, glob@^7.1.3:
   version "7.1.4"
   resolved "https://registry.yarnpkg.com/glob/-/glob-7.1.4.tgz#aa608a2f6c577ad357e1ae5a5c26d9a8d1969255"
@@ -2446,6 +2486,13 @@ is-arrayish@^0.2.1:
   resolved "https://registry.yarnpkg.com/is-arrayish/-/is-arrayish-0.2.1.tgz#77c99840527aa8ecb1a8ba697b80645a7a926a9d"
   integrity sha1-d8mYQFJ6qOyxqLppe4BkWnqSap0=
 
+is-binary-path@~2.1.0:
+  version "2.1.0"
+  resolved "https://registry.yarnpkg.com/is-binary-path/-/is-binary-path-2.1.0.tgz#ea1f7f3b80f064236e83470f86c09c254fb45b09"
+  integrity sha512-ZMERYes6pDydyuGidse7OsHxtbI7WVeUEozgR/g7rd0xUimYNlvZRE/K2MgZTjWy725IfelLeVcEM97mmtRGXw==
+  dependencies:
+    binary-extensions "^2.0.0"
+
 is-buffer@^1.1.5:
   version "1.1.6"
   resolved "https://registry.yarnpkg.com/is-buffer/-/is-buffer-1.1.6.tgz#efaa2ea9daa0d7ab2ea13a97b2b8ad51fefbe8be"
@@ -2534,7 +2581,7 @@ is-generator-fn@^2.0.0:
   resolved "https://registry.yarnpkg.com/is-generator-fn/-/is-generator-fn-2.1.0.tgz#7d140adc389aaf3011a8f2a2a4cfa6faadffb118"
   integrity sha512-cTIB4yPYL/Grw0EaSzASzg6bBy9gqCofvWN8okThAYIxKJZC+udlRAmGbM0XLeniEJSs8uEgHPGuHSe1XsOLSQ==
 
-is-glob@^4.0.1:
+is-glob@^4.0.1, is-glob@~4.0.1:
   version "4.0.1"
   resolved "https://registry.yarnpkg.com/is-glob/-/is-glob-4.0.1.tgz#7567dbe9f2f5e2467bc77ab83c4a29482407a5dc"
   integrity sha512-5G0tKtBTFImOqDnLB2hG6Bp2qcKEFduo4tZu9MT/H6NQv/ghhy30o55ufafxJ/LdH79LLs2Kfrn85TLKyA7BUg==
@@ -3547,6 +3594,11 @@ normalize-path@^2.1.1:
   dependencies:
     remove-trailing-separator "^1.0.1"
 
+normalize-path@^3.0.0, normalize-path@~3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/normalize-path/-/normalize-path-3.0.0.tgz#0dcd69ff23a1c9b11fd0978316644a0388216a65"
+  integrity sha512-6eZs5Ls3WtCisHWp9S2GUy8dqkpGi4BVSz3GaqiE6ezub0512ESztXUwUB6C6IKbQkY2Pnb/mD4WYojCRwcwLA==
+
 npm-bundled@^1.0.1:
   version "1.0.6"
   resolved "https://registry.yarnpkg.com/npm-bundled/-/npm-bundled-1.0.6.tgz#e7ba9aadcef962bb61248f91721cd932b3fe6bdd"
@@ -3870,6 +3922,11 @@ performance-now@^2.1.0:
   resolved "https://registry.yarnpkg.com/performance-now/-/performance-now-2.1.0.tgz#6309f4e0e5fa913ec1c69307ae364b4b377c9e7b"
   integrity sha1-Ywn04OX6kT7BxpMHrjZLSzd8nns=
 
+picomatch@^2.0.4:
+  version "2.1.0"
+  resolved "https://registry.yarnpkg.com/picomatch/-/picomatch-2.1.0.tgz#0fd042f568d08b1ad9ff2d3ec0f0bfb3cb80e177"
+  integrity sha512-uhnEDzAbrcJ8R3g2fANnSuXZMBtkpSjxTTgn2LeSiQlfmq72enQJWdQllXW24MBLYnA1SBD2vfvx2o0Zw3Ielw==
+
 picomatch@^2.0.5:
   version "2.0.7"
   resolved "https://registry.yarnpkg.com/picomatch/-/picomatch-2.0.7.tgz#514169d8c7cd0bdbeecc8a2609e34a7163de69f6"
@@ -4049,6 +4106,13 @@ readable-stream@^2.0.1, readable-stream@^2.0.6:
     string_decoder "~1.1.1"
     util-deprecate "~1.0.1"
 
+readdirp@~3.2.0:
+  version "3.2.0"
+  resolved "https://registry.yarnpkg.com/readdirp/-/readdirp-3.2.0.tgz#c30c33352b12c96dfb4b895421a49fd5a9593839"
+  integrity sha512-crk4Qu3pmXwgxdSgGhgA/eXiJAPQiX4GMOZZMXnqKxHX7TaoL+3gQVo/WeuAiogr07DpnfjIMpXXa+PAIvwPGQ==
+  dependencies:
+    picomatch "^2.0.4"
+
 realpath-native@^1.1.0:
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/realpath-native/-/realpath-native-1.1.0.tgz#2003294fea23fb0672f2476ebe22fcf498a2d65c"