A low-cost 1 × 4 phased array incorporating continuously tunable substrate integrated waveguide (SIW) phase shifters is presented in this paper. Through seamless integration between antenna elements, phase shifters, and a SIW feeding network, the proposed phased array is assembled in a multilayered monolithic structure. To obtain a wide phase variation range, the electronically controllable phase shifter is constructed by introducing varactor diodes into a reflection-type architecture, which can also offer a simple solution to constitute the biasing circuit of the diodes. Due to the merits of adequate bandwidth and good radiation performance, an aperture-coupled patch antenna with multi-resonance characteristic is selected as the array element. Accordingly, a prototype of the proposed phased array was fabricated by applying standard printed circuit board (PCB) facilities. Measured results demonstrate that a continuous beam scanning range from -45° to 45° covering the whole operating band of 5.09-5.98 GHz is obtained. Meanwhile, a gain of up to 11 dBi and an impedance bandwidth of 16.1% are achieved. Owing to the features of continuous wide-angle steerable beam, easy fabrication and integration, the proposed phased-array antenna is attractive for 5G Wi-Fi applications.