This paper investigates a dual-band direct up-conversion mixer operating at 5G millimeter-wave (mmW) bands. To prove the concept, the mixer is implemented in a 22nm FDSOI technology. A Gilbert cell was applied for the mixer core to achieve a high local oscillator signal (LO) suppression. An active balun was integrated on-chip to manage and optimize the LO phase- and magnitude-mismatch. Dual-band and broadband matching networks enable dual-band operation. The mixer has a total power consumption of 38mW including the LO active balun, mixer core and RF output buffer. The measurements show a conversion gain of −2.6 dB and −1 dB and a 1-dB output compression point (oP1dB) of −2.5 dBm and −0.6 dBm at 28 GHz and 38 GHz bands, respectively. The core area of the design is 0.24 mm 2 . The mixer compares well against other designs operating at 5GmmW bands by showing one of the highest oP1dB, a comparable conversion gain and power consumption. To the best knowledge of the authors, this is the first 5G dual-band up-conversion mixer from technology node 22nm and below.