In this paper, an endfire dual-polarized phased array is introduced for 5G mobile applications, which operates from 26 GHz to 30 GHz with low profile of only 1.1 mm (0.1 λ₀ at 26 GHz) and small clearance of 3.5 mm. The array consists of interleaved substrate integrated waveguide (SIW) based vertical-polarized elements and notch type horizontal-polarized elements. The bandwidth of each SIW element is greatly improved by introducing a wide-band impedance transition, which is composed by parallel plate resonators and a metallic via in between. The notch elements have very compact size, which helps to keep the half-wavelength inter-element distance. The array has a planar structure and is easy to fabricate. The measured and simulated results align well with each other.