diff --git a/src/EnvironmentSetCommand.php b/src/EnvironmentSetCommand.php
index 5f53c38..a6128f6 100644
--- a/src/EnvironmentSetCommand.php
+++ b/src/EnvironmentSetCommand.php
@@ -2,6 +2,7 @@
 
 namespace ImLiam\EnvironmentSetCommand;
 
+use Carbon\Carbon;
 use Illuminate\Console\Command;
 use Illuminate\Support\Facades\App;
 use Illuminate\Support\Str;
@@ -76,10 +77,16 @@ public function handle(): void
      */
     public function setEnvVariable(string $envFileContent, string $key, string $value): array
     {
-        // For existed key.
+        // For existing key.
         $oldKeyValuePair = $this->readKeyValuePair($envFileContent, $key);
+
         if ($oldKeyValuePair !== null) {
-            return [str_replace($oldKeyValuePair, $key . '=' . $value, $envFileContent), false];
+            $historyString = $this->getHistoryString($oldKeyValuePair);
+
+            $oldKeyValuePair = preg_quote($oldKeyValuePair);
+            $updatedContent = preg_replace("/^{$oldKeyValuePair}[^\r\n]*/m", $historyString . $key . '=' . $value, $envFileContent);
+
+            return [$updatedContent, false];
         }
 
         // For a new key.
@@ -182,4 +189,22 @@ protected function writeFile(string $path, string $contents): bool
     {
         return (bool)file_put_contents($path, $contents, LOCK_EX);
     }
+
+    /**
+     * Add history to a file.
+     *
+     * @param string $keyValuePair
+     *
+     * @return string
+     */
+    public function getHistoryString(string $oldKeyValuePair = null): string
+    {
+        if (!env('ENVSET_HISTORY', false) || $oldKeyValuePair === null) {
+            return '';
+        }
+
+        $date = Carbon::now()->format('Y-m-d H:i:s');
+
+        return "# {$oldKeyValuePair} # Edited: {$date}\n";
+    }
 }
diff --git a/tests/Unit/EnvironmentSetCommandTest.php b/tests/Unit/EnvironmentSetCommandTest.php
index 1b25eb5..42ad38c 100644
--- a/tests/Unit/EnvironmentSetCommandTest.php
+++ b/tests/Unit/EnvironmentSetCommandTest.php
@@ -2,6 +2,7 @@
 
 namespace Tests\Unit;
 
+use Carbon\Carbon;
 use ImLiam\EnvironmentSetCommand\EnvironmentSetCommand;
 use InvalidArgumentException;
 use PHPUnit\Framework\TestCase;
@@ -85,6 +86,25 @@ public function testAssertKeyIsValid(string $key, bool $isGood): void
         $this->assertTrue($this->command->assertKeyIsValid($key));
     }
 
+    /**
+     * @covers EnvironmentSetCommand::getHistoryString
+     */
+    public function testHistoryString(): void
+    {
+        $this->assertEquals('', $this->command->getHistoryString('old_key=old_value'));
+
+        putenv('ENVSET_HISTORY=true');
+
+        Carbon::setTestNow('2020-01-01 12:00:00');
+
+        $this->assertEquals(
+            "# old_key=old_value # Edited: 2020-01-01 12:00:00\n",
+            $this->command->getHistoryString('old_key=old_value')
+        );
+
+        putenv('ENVSET_HISTORY');
+    }
+
     /**
      * @return array
      * @see EnvironmentSetCommandTest::testSetEnvVariable