Reverse total shoulder arthroplasty (RTSA) is a treatment option for patients with rotator cuff tear arthropathy, pseudoparalysis, and a functional deltoid. Our hypothesis was that no significant difference in postoperative active range of motion (ROM) will be observed in patients with 135° and 155° humeral cup inclination. A systematic review was registered with PROSPERO and performed with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies evaluating RTSA that reported the type of prosthesis as well as active postoperative ROM were eligible for inclusion. Minimum follow-up was 12 months. Pre- and postoperative ROM (and difference, ▵) was compared between RTSA humeral components with cup inclination 135° and 155°. Descriptive statistics were calculated, and the 2 groups were compared using 2-proportion z-test. Sixty-five studies with 3302 patients (3434 shoulders; 1211 in the 135° group and 2223 in the 155° group) were included. Mean patient age was 71.1 ± 7.6 years, 71% were female, and mean follow-up was 37.2 ± 16.5 months. No significant difference existed between patient age at the time of surgery; the average age of patients in the 135° lateralized glenosphere group was 71.67 ± 3.8 years, while the average age of patients in the 155° group was 70.97 ± 8.8 years. Forward elevation, abduction, and external rotation all significantly improved following surgery in the 135° and 155° groups (P < .05). Patients in the 135° group had significantly greater improvement in external rotation (P < .001) and significantly more overall external rotation compared to the 155° group (P < .001). No significant difference existed between 135° and 155° groups in ROM improvements (▵) in forward elevation (P = .142) or abduction (P = .217). Patients with a 135° humeral cup inclination in RTSA gain significantly more external rotation from pre- to postsurgery and have an overall greater amount of external rotation than patients who receive a 155° prosthesis.