In this paper, 2-elements and 4-elements substrate integrated waveguide (SIW) based leaky-wave array antennas are presented and their performances are compared. The enhanced gain and scan angles for 2-elements are 15.4 dBi and 45° respectively and for 4-elements the same is 18.4 dBi and 30° respectively. In the final design of 4-elements array antenna, sinusoidal variation of slot length is used to reduce the side lobe level (SLL). A 1×4 cascaded SIW power divider with effective matching port is used to feed the antenna. Simulations of the antennas are carried out using HFSS software and presented here. © 2015 IEEE.