The current study investigates the effects of streamwise pulsed injections on the mixing performance of a supersonic ejector operating at the critical regime. Streamwise injections are alternatively pulsed at the top and bottom sides of the mixing chamber which oscillates the primary jet. This enhances the bulk mixing between the primary and secondary streams. The mixing enhancement technique resulted in the secondary stream penetrating the primary flow much upstream and the location of the onset of mixing moved upstream by 65.36%. In addition, the larger spread of the primary core flow indicated better mixing performance. The amplitude of oscillation of the primary jet decreased with an increase in the pulsation frequency in the entrance region of the mixing chamber due to the reduced time available for the jet deflection. On the other hand, the amplitude of oscillation of the primary jet remained similar towards the downstream regions of the mixing chamber mainly limited by the physical height of the mixing chamber.