Introduction Concussion is regularly observed in rugby union and has generated a growing public health concern, yet remains one of the least understood injuries facing the sports medicine community. Evidence suggests that multiple concussions may increase susceptibility to long-term neurological complications that present decades after the initial injury for reasons that remain unclear. We aimed to determine the incidence rate and risk factors for concussion amongst community-level rugby union-15s players active during the 1980s given that it may help to better understand the risks and mechanisms of injury. Methods Injury data were collected from clubs by the coach at the time of injury in players using a 15-item questionnaire (1982–1984). Results Seventy games were recorded throughout 1982–1983 and 1983–1984 rugby union seasons. Forty-two documented concussions accounted for ∼6% of injuries corresponding to an incidence rate of 0.64 per 1000 playing hours, more than a third lower than the ‘modern-day’ equivalent. Tackling (relative risk 1.60, p < 0.05), collisions (relative risk 0.95, p < 0.05) and gum shield use (relative risk 1.69, p < 0.05) were independently associated with concussion whereas no associations were observed for ground condition, quarter of play or players playing out of position (p > 0.05). Conclusion Despite limitations due to the retrospective focus and reliance on questionnaire data notwithstanding raised awareness of concussion, the incidence rate of concussion during the 1980s appears to be appreciably lower compared to the present-day game. This is the likely outcome of improvements in the clinical understanding of concussion, data collection tools, reporting methods and clinical management of concussive injuries, including changes to both player and game. However, the findings of this study help better understand the risks and mechanisms of injury once encountered by rugby union players active during the 1980s, of which some of those risks are still apparent.