There are concerns that the field of sport and exercise psychology is limited by insufficient consideration for the demographic, socioeconomic and cultural identities and experiences of participants. This study specifically quantified gender balance among sport and exercise psychology samples for the very first time. Articles published within five leading journals in the field across three separate years (2010, 2015, 2020) were included. Across the 627 studies, data were collected from 258,160 participants. Of these, 138,133 were men/boys (54%), 119,398 were women/girls (46%), and 629 were non-binary or not reported (0.2%; 432 not reported, 197 identified as non-binary or another gender). We demonstrated that studies which focused on sportrather than exercisepsychology, significantly under-represented women/girls. Specifically, the OR for sport as compared to exercise, was 4.94 (95% CI = 3.19-7.64, p < .001), suggesting a markedly increased likelihood of male participation. Nearly one in five studies in sport psychology included exclusively male participants, compared to just 7% with females. Studies conducted in Europe, as well as those exploring interventions and experimental research, were also associated with an over-representation of male participants. Important questions are raised as to the conduct of representative research in the field of applied sport psychology, with recommendations provided.