This paper presents an experimental study on effect of Strouhal number on heat transfer characteristics of a round synthetic jet (SJ). The motivation of the present work is to utilize the maximum efficiency of a synthetic jet for impingement cooling. In this view, the SJ is operated in a manner that vortices formed at the orifice impinged on the surface with their natural frequency of the vortex formation. In the present set of experiments, the Strouhal number (St) is varied from 0.1 − 0.8. For these values of St, the experiments are carried out for the non-dimensionalized jet to surface spacing (z/d) of 3, 6, 10 and 16. The Reynolds number (Re) is kept constant at 1920 for the first part of the experiment. For the second part, Re is kept constant at 2200, and the amplitude of the oscillating diaphragm is also kept constant corresponding to input voltage of 4V. The results show that the jet impingement at a constant Re provides the highest value of the heat transfer coefficient at a particular combination of the jet diameter, jet velocity and operating frequency (Strouhal number). Also, for a lower surface spacing, a maximum value of heat transfer is obtained for the larger value of the St. Whereas, for the higher surface spacing, a maximum heat transfer rate is observed for the lower St.