diff --git a/config/initializers/deprecation_warning_subscriber.rb b/config/initializers/deprecation_warning_subscriber.rb
new file mode 100644
index 00000000000..89ee7dafced
--- /dev/null
+++ b/config/initializers/deprecation_warning_subscriber.rb
@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+# @note For use in conjuction with setting `Rails.application.config.active_support.deprecation = :notify`.
+#   Whenever a “deprecation.rails” notification is published, it will dispatch the event
+#   (ActiveSupport::Notifications::Event) to method #deprecation.
+class DeprecationWarningSubscriber < ActiveSupport::Subscriber
+  APP_NAME = "caseflow"
+  SLACK_ALERT_CHANNEL = "#appeals-deprecation-alerts"
+
+  attach_to :rails
+
+  def deprecation(event)
+    emit_warning_to_application_logs(event)
+    emit_warning_to_sentry(event)
+    emit_warning_to_slack_alerts_channel(event)
+  rescue StandardError => error
+    Raven.capture_exception(error)
+  end
+
+  private
+
+  def emit_warning_to_application_logs(event)
+    Rails.logger.warn(event.payload[:message])
+  end
+
+  def emit_warning_to_sentry(event)
+    # Pre-emptive bugfix for future versions of the `sentry-raven` gem:
+    #   Need to convert callstack elements from `Thread::Backtrace::Location` objects to `Strings`
+    #   to avoid a `TypeError` on `options.deep_dup` in `Raven.capture_message`:
+    #   https://github.com/getsentry/sentry-ruby/blob/2e07e0295ba83df4c76c7bf3315d199c7050a7f9/lib/raven/instance.rb#L114
+    callstack_strings = event.payload[:callstack].map(&:to_s)
+
+    Raven.capture_message(
+      event.payload[:message],
+      level: "warning",
+      extra: {
+        message: event.payload[:message],
+        gem_name: event.payload[:gem_name],
+        deprecation_horizon: event.payload[:deprecation_horizon],
+        callstack: callstack_strings,
+        environment: Rails.env
+      }
+    )
+  end
+
+  def emit_warning_to_slack_alerts_channel(event)
+    slack_alert_title = "Deprecation Warning - #{APP_NAME} (#{ENV['DEPLOY_ENV']})"
+
+    SlackService
+      .new(url: ENV["SLACK_DISPATCH_ALERT_URL"])
+      .send_notification(event.payload[:message], slack_alert_title, SLACK_ALERT_CHANNEL)
+  end
+end
diff --git a/spec/initializers/deprecation_warning_subscriber_spec.rb b/spec/initializers/deprecation_warning_subscriber_spec.rb
new file mode 100644
index 00000000000..57e88778983
--- /dev/null
+++ b/spec/initializers/deprecation_warning_subscriber_spec.rb
@@ -0,0 +1,84 @@
+# frozen_string_literal: true
+
+describe "DeprecationWarningSubscriber" do
+  let(:rails_logger) { Rails.logger }
+  let(:slack_service) { SlackService.new(url: "dummy-url") }
+
+  before do
+    allow(Rails).to receive(:logger).and_return(rails_logger)
+    allow(rails_logger).to receive(:warn)
+
+    allow(Raven).to receive(:capture_message)
+    allow(Raven).to receive(:capture_exception)
+
+    allow(SlackService).to receive(:new).with(url: anything).and_return(slack_service)
+    allow(slack_service).to receive(:send_notification)
+  end
+
+  context "when a 'deprecation.rails' event is instrumented" do
+    let(:app_name) { "caseflow" }
+    let(:deploy_env) { ENV["DEPLOY_ENV"] }
+    let(:payload) do
+      {
+        message: "test message",
+        gem_name: "Rails",
+        deprecation_horizon: "6.0",
+        callstack: [location_1, location_2]
+      }
+    end
+    let(:location_1) { instance_double("Thread::Backtrace::Location", to_s: "location 1") }
+    let(:location_2) { instance_double("Thread::Backtrace::Location", to_s: "location 2") }
+
+    def instrument_deprecation_warning
+      ActiveSupport::Notifications.instrument("deprecation.rails", payload)
+    end
+
+    it "emits a warning to the application logs" do
+      instrument_deprecation_warning
+
+      expect(rails_logger).to have_received(:warn).with(payload[:message])
+    end
+
+    it "emits a warning to Sentry" do
+      instrument_deprecation_warning
+
+      expect(Raven).to have_received(:capture_message).with(
+        payload[:message],
+        level: "warning",
+        extra: {
+          message: payload[:message],
+          gem_name: "Rails",
+          deprecation_horizon: "6.0",
+          callstack: ["location 1", "location 2"],
+          environment: Rails.env
+        }
+      )
+    end
+
+    it "emits a warning to Slack channel" do
+      slack_alert_title = "Deprecation Warning - #{app_name} (#{deploy_env})"
+
+      instrument_deprecation_warning
+
+      expect(slack_service).to have_received(:send_notification).with(
+        payload[:message],
+        slack_alert_title,
+        "#appeals-deprecation-alerts"
+      )
+    end
+
+    context "when an exception occurs" do
+      before { allow(slack_service).to receive(:send_notification).and_raise(StandardError) }
+
+      it "logs error to Sentry" do
+        instrument_deprecation_warning
+
+        expect(Raven).to have_received(:capture_exception).with(StandardError)
+      end
+
+      it "does not raise error" do
+        expect { instrument_deprecation_warning }.not_to raise_error
+      end
+    end
+  end
+end