This paper presents a broadband, dual-polarized substrate integrated waveguide cavity-backed slot antenna. In this design, high-order cavity resonances are used to generate arbitrary levels of inclined linear polarization. The antenna can provide an adjustable inclined linearly polarized with an aspect ratio of E x /E y ranging from 0.11 to 0.69. The proposed antenna provides fractional impedance bandwidth of 11% with at least front-to-back ratio of 10 dB in broadside direction and a relative gain of 6 dBi at most of the operating impedance bandwidth. The antenna structure is numerically evaluated using High Frequency Structure Simulator and results including reflection coefficient, axial ratio, and radiation patterns are reported.