Abstract: An auxiliary signal device for a mailbox includes a signal flag pivotally supported on a bracket mounted near the rear of the mailbox. An operating rod connected to another bracket mounted on the mailbox door cams the signal flag and catapults it to a raised position when the door is opened. A detent retains the signal flag in its raised position until it is lowered by manually operating a lowering rod. The signal device is attached to a mailbox by bending mounting tabs on the brackets into engagement with associated surfaces of the mailbox.