In this paper a bi-band quasi Yagi Uda antenna is presented. The antenna prototype is designed for the 24.25 GHz-28.5 GHz frequency band and 47.2 GHz-48.2 GHz frequency band. The second frequency band of operation is obtained by two slots added in the radiator, a patterned ground plane and 3 sets of radiators. Simulations show a 8 dB maximum in the lower band and 8.5 dB in the higher band. A prototype has been realized on 250 µm thick Taconic RF35 (tan δ = 0.0019 and ϵ r = 3.5) substrate with 17 µm two thick copper layers. The size of the prototype is 15 x 20 mm 2. Measurements show a bi-band behavior with 8.5 dB in the gain and 8.2 dB gain in the lower band and 8.5 dB in the highest band. A mismatch of 2 GHz is observed between measurements and simulations in the highest band.