Background: Healing failure after rotator cuff repair is a challenging problem. Acute, trauma-related tears are considered a separate entity and are often treated surgically. The aim of this study was to identify factors associated with healing failure in previously asymp-tomatic patients with trauma-related rotator cuff tears treated with early arthroscopic repair. Methods: This study included 62 consecutively recruited patients (23% women; median age, 61 years; age range, 42-75 years) with acute symptoms in a previously asymptomatic shoulder and a magnetic resonance imaging-verified full-thickness rotator cuff tear after shoulder trauma. All patients were offered, and underwent, early arthroscopic repair, during which a biopsy specimen was har-vested from the supraspinatus tendon and analyzed for signs of degeneration. Of the patients, 57 (92%) completed 1-year follow-up and underwent assessment of repair integrity on magnetic resonance images according to the Sugaya classification. Risk factors for heal-ing failure were investigated using a causal-relation diagram where age, body mass index, tendon degeneration (Bonar score), diabetes mellitus, fatty infiltration (FI), sex, smoking, tear location regarding integrity of the rotator cable, and tear size (number of ruptured tendons and tendon retraction) were included and analyzed. Results: Healing failure at 1 year was identified in 37% of patients (n = 21). A high degree of FI of the supraspinatus muscle (P = .01), a tear location including disruption of rotator cable integrity (P = .01), and old age (P = .03) were associated with healing failure. Tendon degeneration as determined by histopathology was not associated with healing failure at 1-year follow-up (P = .63). Conclusion: Older age, increased FI of the supraspinatus muscle, and a tear including disruption of the rotator cable increased the risk of healing failure after early arthroscopic repair in patients with trauma-related full-thickness rotator cuff tears. Level of evidence: Level I; Prospective Cohort Design; Prognosis Study