diff --git a/src/Cli/dotnet/Program.cs b/src/Cli/dotnet/Program.cs

index de1ebb9e6..6bbf479de 100644

--- a/src/Cli/dotnet/Program.cs

+++ b/src/Cli/dotnet/Program.cs

@@ -28,6 +28,13 @@ public class Program

         public static int Main(string[] args)

         {

+            // opt out of telemetry by default if the env var is unset

+            string telemetryValue = Environment.GetEnvironmentVariable("DOTNET_CLI_TELEMETRY_OPTOUT");

+            if (String.IsNullOrEmpty(telemetryValue))

+            {

+                Environment.SetEnvironmentVariable("DOTNET_CLI_TELEMETRY_OPTOUT", "1");

+            }

+

             DebugHelper.HandleDebugSwitch(ref args);

             // Capture the current timestamp to calculate the host overhead.