This paper presents a 21.5-to-36 GHz 6-bit radio frequency variable gain amplifier (RF-VGA) for the fifth generation (5G) communication phased-arrays in 0.13-µm SiGe BiCMOS technology. To maintain a wideband stable power gain and accurate gain control under all operation states, the two-stage amplifier comprising a cascode amplifier with RC compensating network and a common emitter amplifier is designed and realized. The measured results reveal a wide gain tuning range of -16 to 16 dB, a gain resolution of 0.5 dB with 6-bit digital control, a minimum RMS gain error of 0.04 dB only, 3-dB bandwidth of 13.5 GHz, output P1dB compression point of 9.3 dBm, and total DC power consumption of 23.5 mW under 1.6V supply. The chip area is 0.64×0.4 mm2 excluding the testing pads. To the best of the authors’ knowledge, it achieves the best FOM among similar reported VGAs.