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 wavelength 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.