In this paper, a compact tri-band printed multi-input multi-output (MIMO) antenna with high isolation is presented to operate within WLAN and WiMAX frequency bands. By adopting a rectangular open-ended slot combined with a rectangular strip with an inverted L-shaped open-ended slot, three operating frequency bands can be obtained. The proposed compact MIMO antenna occupies an overall size of 19×33 mm2. Good port-to-port isolation is obtained. The simulated and measured results show that the presented antenna is suitable for multiband MIMO applications.