diff --git a/src/test/mock/clitools.rs b/src/test/mock/clitools.rs
index fe5f834844b..1c115561cae 100644
--- a/src/test/mock/clitools.rs
+++ b/src/test/mock/clitools.rs
@@ -547,6 +547,17 @@ impl Config {
         }
     }
 
+    #[track_caller]
+    pub fn expect_stdout_ok_with_env(&self, args: &[&str], env: &[(&str, &str)], expected: &str) {
+        let out = self.run(args[0], &args[1..], env);
+        if !out.ok || !out.stdout.contains(expected) {
+            print_command(args, &out);
+            println!("expected.ok: true");
+            print_indented("expected.stdout.contains", expected);
+            panic!();
+        }
+    }
+
     #[track_caller]
     pub fn expect_not_stdout_ok(&self, args: &[&str], expected: &str) {
         let out = self.run(args[0], &args[1..], &[]);
diff --git a/tests/suite/cli_rustup.rs b/tests/suite/cli_rustup.rs
index 9a6adde7a4d..74aa7221366 100644
--- a/tests/suite/cli_rustup.rs
+++ b/tests/suite/cli_rustup.rs
@@ -2376,6 +2376,130 @@ fn only_toml_in_rust_toolchain_toml() {
     });
 }
 
+/// Checks that `rust-toolchain.toml` configs can be overridden by `rustup override set` or `<proxy> +<toolchain>`.
+/// See: <https://github.com/rust-lang/rustup/issues/3483>
+#[test]
+fn rust_toolchain_toml_with_rustup_override() {
+    test(&|config| {
+        config.with_scenario(Scenario::SimpleV2, &|config| {
+            config.expect_ok(&["rustup", "default", "stable"]);
+
+            let stable = "hash-stable-1.1.0";
+            config.expect_stdout_ok(&["rustc", "--version"], stable);
+
+            config.expect_ok(&["rustup", "override", "set", "beta"]);
+
+            let cwd = config.current_dir();
+            let toolchain_file = cwd.join("rust-toolchain.toml");
+            raw::write_file(
+                &toolchain_file,
+                r#"
+                    [toolchain]
+                    channel = "nightly"
+                    components = [ "rls" ]
+                "#,
+            )
+            .unwrap();
+
+            let beta = "hash-beta-1.2.0";
+            config.expect_stdout_ok(&["rustc", "--version"], beta);
+            config.expect_stdout_ok(&["rls", "--version"], beta);
+
+            config.expect_stderr_ok(&["rls", "+stable", "--version"], stable);
+        })
+    });
+}
+
+/// Checks that `rust-toolchain.toml` configs can be overridden by `RUSTUP_TOOLCHAIN`.
+/// See: <https://github.com/rust-lang/rustup/issues/3483>
+#[test]
+fn rust_toolchain_toml_with_rustup_toolchain() {
+    test(&|config| {
+        config.with_scenario(Scenario::SimpleV2, &|config| {
+            config.expect_err(
+                &["rustc", "--version"],
+                "rustup could not choose a version of rustc to run",
+            );
+
+            let cwd = config.current_dir();
+            let toolchain_file = cwd.join("rust-toolchain.toml");
+            raw::write_file(
+                &toolchain_file,
+                r#"
+                    [toolchain]
+                    channel = "nightly"
+                    components = [ "rls" ]
+                "#,
+            )
+            .unwrap();
+
+            let env = &[("RUSTUP_TOOLCHAIN", "beta")];
+            let beta = "hash-beta-1.2.0";
+            config.expect_stdout_ok_with_env(&["rustc", "--version"], env, beta);
+            config.expect_stdout_ok_with_env(&["rls", "--version"], env, beta);
+
+            // At this point, `nightly` is still NOT installed.
+            config.expect_not_stderr_ok(&["rustup", "toolchain", "list"], "nightly");
+        })
+    });
+}
+
+/// Checks that `rust-toolchain.toml` configs can override `rustup override set` at different directories.
+/// See: <https://github.com/rust-lang/rustup/issues/3483>
+#[test]
+fn rust_toolchain_toml_with_rustup_override_parent_dir() {
+    test(&|config| {
+        config.with_scenario(Scenario::SimpleV2, &|config| {
+            config.expect_err(
+                &["rustc", "--version"],
+                "rustup could not choose a version of rustc to run",
+            );
+
+            // "." -> nightly, no rls
+            config.expect_ok(&["rustup", "override", "set", "nightly"]);
+
+            // "./inner" -> beta + rls
+            let inner = &config.current_dir().join("inner");
+            std::fs::create_dir(inner).unwrap();
+            config.change_dir(inner, &|config| {
+                let cwd = config.current_dir();
+                let toolchain_file = cwd.join("rust-toolchain.toml");
+                raw::write_file(
+                    &toolchain_file,
+                    r#"
+                    [toolchain]
+                    channel = "beta"
+                    components = [ "rls" ]
+                "#,
+                )
+                .unwrap();
+
+                let beta = "hash-beta-1.2.0";
+                config.expect_stdout_ok(&["rustc", "--version"], beta);
+                config.expect_stdout_ok(&["rls", "--version"], beta);
+            });
+
+            // "./inner/inner" -> stable, no rls
+            let inner2 = &inner.join("inner");
+            std::fs::create_dir(inner2).unwrap();
+            config.change_dir(inner2, &|config| {
+                config.expect_ok(&["rustup", "override", "set", "stable"]);
+
+                let stable = "hash-stable-1.1.0";
+                config.expect_stdout_ok(&["rustc", "--version"], stable);
+                // The `rustup override set` in this directory stops
+                // the `rust-toolchain.toml` in the parent directory from working.
+                config.expect_component_not_executable("rls")
+            });
+
+            // "." -> nightly, no rls
+            let nightly = "hash-nightly-2";
+            config.expect_stdout_ok(&["rustc", "--version"], nightly);
+            config.expect_component_not_executable("rls");
+        })
+    });
+}
+
 /// Checks that a warning occurs if both `rust-toolchain` and `rust-toolchain.toml` files exist
 #[test]
 fn warn_on_duplicate_rust_toolchain_file() {