diff --git a/cli/args/mod.rs b/cli/args/mod.rs
index 950ba72e25..04a0111961 100644
--- a/cli/args/mod.rs
+++ b/cli/args/mod.rs
@@ -1660,6 +1660,34 @@ impl CliOptions {
       });
     }
 
+    if !from_config_file.is_empty() {
+      // collect unstable granular flags
+      let mut all_valid_unstable_flags: Vec<&str> =
+        crate::UNSTABLE_GRANULAR_FLAGS
+          .iter()
+          .map(|granular_flag| granular_flag.0)
+          .collect();
+
+      let mut another_unstable_flags =
+        Vec::from(["sloppy-imports", "byonm", "bare-node-builtins"]);
+      // add more unstable flags to the same vector holding granular flags
+      all_valid_unstable_flags.append(&mut another_unstable_flags);
+
+      // check and warn if the unstable flag of config file isn't supported, by
+      // iterating through the vector holding the unstable flags
+      for unstable_value_from_config_file in &from_config_file {
+        if !all_valid_unstable_flags
+          .contains(&unstable_value_from_config_file.as_str())
+        {
+          log::warn!(
+            "{} '{}' isn't a valid unstable feature",
+            colors::yellow("Warning"),
+            unstable_value_from_config_file
+          );
+        }
+      }
+    }
+
     from_config_file
   }
 
diff --git a/tests/specs/task/invalid_unstable_feature/__test__.jsonc b/tests/specs/task/invalid_unstable_feature/__test__.jsonc
new file mode 100644
index 0000000000..bfac9d1536
--- /dev/null
+++ b/tests/specs/task/invalid_unstable_feature/__test__.jsonc
@@ -0,0 +1,6 @@
+{
+  "steps": [{
+    "args": "task start",
+    "output": "invalid_unstable_feature.out"
+  }]
+}
diff --git a/tests/specs/task/invalid_unstable_feature/deno.json b/tests/specs/task/invalid_unstable_feature/deno.json
new file mode 100644
index 0000000000..36f084e47d
--- /dev/null
+++ b/tests/specs/task/invalid_unstable_feature/deno.json
@@ -0,0 +1,22 @@
+{
+  "tasks": {
+    "start": "deno run index.js"
+  },
+  "unstable": [
+    "abc",
+    "byonm",
+    "bare-node-builtins",
+    "sloppy-imports",
+    "unsafe-proto",
+    "webgpu",
+    "broadcast-channel",
+    "worker-options",
+    "cron",
+    "kv",
+    "ffi",
+    "fs",
+    "net",
+    "http",
+    "cba"
+  ]
+}
diff --git a/tests/specs/task/invalid_unstable_feature/index.js b/tests/specs/task/invalid_unstable_feature/index.js
new file mode 100644
index 0000000000..fb5a295b66
--- /dev/null
+++ b/tests/specs/task/invalid_unstable_feature/index.js
@@ -0,0 +1 @@
+console.log("Hello unstable features");
diff --git a/tests/specs/task/invalid_unstable_feature/invalid_unstable_feature.out b/tests/specs/task/invalid_unstable_feature/invalid_unstable_feature.out
new file mode 100644
index 0000000000..78c4eaca9f
--- /dev/null
+++ b/tests/specs/task/invalid_unstable_feature/invalid_unstable_feature.out
@@ -0,0 +1,5 @@
+Task start deno run index.js
+Warning Sloppy imports are not recommended and have a negative impact on performance.
+Warning 'abc' isn't a valid unstable feature
+Warning 'cba' isn't a valid unstable feature
+Hello unstable features