Abstract: A portable sliding window lock consists of a molded resilient triangular block having a suction cup securely fastened to its base. The suction cup is fastened to the base so that a jamming tapered tip on the triangular block is angled slightly toward the mounting surface. The portable sliding window lock is mounted on the vertical surface of a flat window pane adjacent the frame of a sliding window to intercept and jam the window frame with the sliding window partially open. This prevents forcing the partially open window any further open to gain access to an area. An optional feature includes an audible alarm mounted on the resilient triangular block which is set-off by a switch activated by force applied to a sliding glass window engaging the resilient triangular block. The audible alarm is activated by a contact switch, motion sensing switch or pressure switch embedded in the molded resilient triangular block.