Void fraction and relative velocity between phases are parameters of key importance when analyzing two-phase flow systems. The drift flux model is a simple, yet robust, method of predicting these parameters. Detailed drift flux analyses have focused on vertical flows, with recent work investigating horizontal flows. There is comparatively little work performed involving inclined two-phase flows—and fewer specifically for inclined bubbly flows. Depending on the orientation, the buoyancy force may not act parallel to the flow direction and can induce asymmetry and bubble clustering, which may affect relative velocity and void fraction. The current work seeks to characterize the effects of inclination on void fraction and relative velocity in bubbly two-phase flows. This is done by performing one-dimensional drift flux analyses and by comparing closure relations proposed in the literature. Experiments are performed focusing on bubbly flows in an inclinable test facility with an inner diameter of 25.4 mm. Time-averaged two-phase flow parameters are measured using four-sensor conductivity probes, and these measurements are benchmarked to ensure reliability. It is found that as the inclination angle is reduced from vertical, the relative velocity changes rapidly, yielding a slip ratio of less than unity for angles investigated below 80°. This corresponds to changes in the distribution parameter and drift velocity. The effects of angle are also apparent in changes in the area-averaged void fraction. These findings challenge previously developed correlations, which are generally unable to predict the experimental void fraction and have suggested slip greater than unity for inclined-upward bubbly flows.