This prospective study evaluated whether the AlignRT surface-guided radiotherapy system improves patient positioning accuracy during stereotactic radiosurgery (SRS) for brain metastases compared with standard manual positioning. Twenty adults scheduled for single-fraction SRS were positioned twice before treatment. Participants were first positioned using the standard manual method with delta couch shift and were then positioned automatically using the AlignRT system. After each positioning method, a partial cone-beam computed tomography (CBCT) scan was performed to measure residual setup deviations in three translational and three rotational directions. The primary objective was to compare the average setup deviations between the two positioning methods and determine whether AlignRT provided more accurate patient positioning. The additional positioning and imaging procedure prolonged the treatment visit by up to 15 minutes and involved a low additional imaging dose.