Purpose <p>Limited evidence exists for functional outcomes of neck-shaft-angle (NSA) in reverse shoulder arthroplasty (RSA) for proximal humerus fractures (PHFs). We evaluated the functional outcomes of 155° versus 145° NSA RSA, to determine superiority for acute PHFs.</p> Method <p>Retrospective analysis of 66-patients with displaced 3/4-part, head-split or fracture-dislocation PHFs, managed with acute RSA, within 4-weeks of injury at single trauma unit. 33-patients underwent 155° NSA RSA cemented stem; 33-patients 145° NSA RSA uncemented stem. All had same glenoid components with equivocal humeral stem retrotorsion and routine reconstructions of tuberosities. Primary outcome was range of motion; with radiological, and patient reported outcome measures (PROMs) as secondary outcomes.</p> Results <p>Median age 72 years. Median follow-up 27 months. Healed greater tuberosity (GT) conferred better outcomes for all. 155° NSA conferred better GT healing, although not significant (93% vs 78%; <i>p </i>= 0.18). 145° NSA achieved significantly better external rotation in adduction (ER1) of 51° vs 32° (<i>p</i> = 0.02) and internal rotation of 7.5 vs 5.4 points (<i>p</i> = 0.03), whilst 155° had greater percentage patients (83% vs 66%) reach functional active elevation (AE) (&gt;130°). Despite an unhealed GT, 145° NSA was still associated with better ER1 (<i>p</i> = 0.04). OSS significantly better in 145°, 44 vs 39 (<i>p</i> = 0.03), with no significant difference across other PROMs. 145° reached minimal clinically important difference for OSS (5-points) and ER1 (5°), whilst conferring substantial clinical benefit for ER1 (11°). Low complication rate for both cohorts (6.06%).</p> Conclusions <p>Both groups provided reliable and satisfactory outcomes in acute management of PHFs. 155° NSA provides better AE and GT healing; 145° NSA achieving better rotational movements, extension and OSS.</p> Level III evidence <p>Retrospective Cohort Comparison; Treatment Study</p>