This article presents a high-performance fully metallic dual-polarized wideband Vivaldi array for the Ka-band (26-40 GHz), which is going to be used, for example, in 5G millimeter-wave (mmWave) communication networks. Antenna-array elements are fed straight from a single printed circuit board (PCB) that allows integrating active components in the immediate proximity of antenna elements. A whole array can be placed on a PCB as a through-hole or surface-mount technology component. The antenna is simulated in a unit cell with periodic boundary conditions and in an 8×8 array configuration. The simulations show that the active reflection coefficient is below -10 dB across the entire Ka-band and throughout most of the beam-steering angles up to ±60°. Lower than 3 dB scan loss is achieved in approximately ±60° range in the elementary planes and ±50° in the diagonal planes. The reflection coefficient and gain of each of the four elements in different parts of the manufactured dual-polarized 8,×8 array were measured and simulated with the remaining elements terminated with a 50Ω load. The measured results follow closely the full-wave finite array simulation results; the reflection coefficient is low and the element pattern is wide over the entire frequency range.