Background: There is little evidence regarding the mechanisms of pectoralis major (PM) injury and player outcomes in Australian Football League (AFL) players. Purposes/Hypothesis: The study aims were to investigate (1) the mechanisms of PM muscle injury in elite AFL players via video analysis and (2) the player profile, method of management, and clinical outcomes of the PM injuries sustained. We hypothesized that the majority of PM tears would occur in outer-range PM positions (hyperextension of the glenohumeral joint). Study Design: Case series; Level of evidence, 4. Methods: We analyzed video of the precipitating event for traumatic PM injuries during AFL competition or training over a 20-year period (2002-2021). The footage was analyzed by 4 experienced assessors, and the following were evaluated: mechanism of injury, injury variables (arm position, initial contact point, visual awareness, and use of taping), player characteristics (age at the time of injury, hand dominance, and history of injury), injury profile (location and size of tear), method of management (operative vs nonoperative), patient outcomes (time to return to full senior training/match play), and complication rates. Results: The mean ± standard deviation age of the players was 26.5 ± 3.1 years (range, 21-32 years). Overall, 22 PM injuries were identified in the AFL injury database for a rate of 1.1 per year; 16 of these injuries had accompanying video footage. We identified 3 mechanisms for PM injury: horizontal hyperextension (62.5%), hyperflexion-abduction (25.0%), and horizontal adduction (sustained tackling; 12.5%). The most common site of the tear was the insertion point of the sternocostal head (91.0%). Twenty players (91.0%) required surgical repair, with 75% undergoing surgery within 1 week (range, 0-26 weeks). The mean return to competition for the surgical repair group was 11.1 weeks (range, 8-15 weeks). The rerupture rate was 5.0% (1 repair; <4 weeks postoperatively in 2004). Conclusion: PM tears in elite male AFL players were due to 1 of 3 distinct mechanisms: horizontal hyperextension, hyperflexion-abduction, and horizontal adduction (sustained tackling). Players returned to play on average 11 weeks after injury. Knowledge regarding mechanisms of injury, player profile, and return-to-sport timelines is important for appropriate medical management and provides potential areas to target for prevention of PM injuries.