In this paper, we present a microwave integrated circuit (MIC) with flip-chip assembled 0.15mm-gate pHEMT. Single transistor (pHEMT of 4´75 mm from WIN Semiconductor) with negative resistance combined with resonant network was designed for Ka-band oscillator. After characterizing the 0.15mm-gate pHEMT, the passive components and CPW connection were designed and fabricated on Al2O3 substrate with consideration of bump transition. The measured output signal was at 27.55 GHz while biasing at VDS = 2 V and ID = 50 mA (VGS = -0.5 V), respectively. The measured signal output power is 1.87 dBm with consideration of cable loss. The corresponding phase noise is -84 dBc/Hz@1MHz offset. To our knowledge, this is the 1st flip-chip assembled pHEMT oscillator using feedback methodology at Ka-band.