BACKGROUND: The effect of fixture congestion on injury rates and patterns has received scarce attention in elite football and existing investigations have not accounted for player rotation or examined the temporal distribution and potential cause of injuries. OBJECTIVE: To prospectively investigate the epidemiology of injury during short periods of fixture congestion in a professional football club. METHODS: Over a six-season period, exposure time and injury data were compared in the same players (n=25 (14 individuals)) when participating in two frequently occurring short congested fixture cycles in comparison to match-play outside these cycles. (1) two successive matches separated by an interval totalling ≤3 days calculated immediately from the end of play in match 1 to the beginning of play in match 2; (2) three successive matches separated by ≤4-day intervals starting the day immediately after each match. RESULTS: In two-match congestion cycles, incidence rate ratios (IRR) showed that there was a higher risk of injury in the final 15 min of play in the second match in comparison to match-play outside the cycles (IRR: 3.1 (95% CI 1.1 to 9.3), p=0.0400). A greater risk of injury overall (IRR: 2.0 (95% CI 1.1 to 3.8), p=0.0345) and in the first-half of play (2.6 (1.1 to 6,5), p=0.0386), and risk of ankle sprains (10.4 (95% CI 1.9 to 57.9), p=0.0068) and non-contact injuries due to a 'change in direction' (IRR: 7.8 (1.3 to 46.8), p=0.0243) were observed in the final match of three-match congestion cycles in comparison to match-play outside the cycles. CONCLUSIONS: Injury rates and patterns were affected in the same elite football players when competing in short congested fixture cycles in comparison to match-play outside the cycles.