This paper presents a 38-GHz 32-element phased-array Tx (transmitter) for the 5G millimeter wave (MMW) communications. The 8-element phased-array Tx modules with 2 GHz IF/5 GHz LO are implemented, and four pieces of the module are stacked to realize an 8×4 brick array. The 38 GHz measurements of the 32-element Tx show 41.8 dBm EIRP at OP1dB with -41.8 dBc image rejection ratio (IMRR) and -35 dBc ×8 LO rejection ratio (×8 LORR). The EIRPs at OP1dB in beam scanning around ±60° azimuth/± 30° elevation planes are 41.8 to 38.3 dBm. The Tx is utilized for data links with a horn antenna module in 35 m that demonstrates 256 QAM/100M-BR (baud rate) with -33.1 dB EVM. The data links of the Tx with a 4-element phased-array Rx (receiver) in 6 m demonstrates 64 QAM/200M-BR with -26.4 dB EVM. The scalable Tx module shows potential for 5G sub-6 GHz/MMW coexistent applications and can be expanded as a massive phased-array using the simple/low-cost stacked methods.