In this paper, we present a compact Doherty power amplifier (DPA) in a 0.15-μm enhancement mode (E-mode) Gallium Arsenide (GaAs) pseudomorphic high electron mobility transistor (pHEMT) process at Ka-band. The 2-stage DPA uses an integrated input broadside coupler to miniaturize the die size to 2.86 mm2. The monolithic millimeter-wave integrated circuit (MMIC) DPA exhibits a measured output power of 26 dBm and a measured average gain of 12 dB. The gain bandwidth covers from 25.5 to 33 GHz. The measured peak power added efficiency (PAE) is 40% and the PAE at 6 dB output power back-off is 29%. Moreover, an adjacent channel power ratio (ACPR) of −45 dBc has been measured using a 20 MHz digitally modulated signal and digital predistortion (DPD).