In this paper, two types of microstrip array antenna for radars operating at 77 GHz are presented. The first type of array antenna is 10×4 elements rectangular patch array antenna with overall size of 20.43mm×7.83 mm. Unit element of this antenna type is a rectangular patch. Series-fed column of 10 unit elements are arranged into 10 × 4 arrays by implementing simple power divider structure. The second type of antenna is 12 × 4 elements leaf array antenna with overall size of 16.72mm×10.75 mm. Unit element of the second antenna type is a rectangular patch that is inclined 45° from the microstrip line axis. Twelve patches are arranged on both sides of the microstrip line and are connected directly at their corners. One additional patch at the end of the structure acts as a matching element. Array consisting of 12×4 unit elements are created by implementing simple power divider structure. Both types of antenna are combined with different types of waveguide-to-microstrip transition consist of two metal layers printed on a single dielectric substrate. The waveguide-to-microstrip transitions are fed by WR10 standard waveguide. The performances of both antennas are verified via simulations and measurements. The rectangular patch array antenna has 19.8 dB gain and 20° × 10° beam width at 77 GHz, while the leaf array antenna has 19.6 dB gain and 19° × 11.6° beam width at 77 GHz. Both types of antenna can be further developed as a reference for designing antenna for radar systems operating at higher frequencies, such as 94 GHz.