Burnout is a psychosocial construct that has been extensively studied in athletes. Burnout is asignificant threat to an athlete’s mental health and increases the risk of dropout from sport(Gustafsson, Madigan, & Lundkvist, 2017). However, little is known about prevalence of clinical-levelsof burnout in athletes. This study therefore aimed to estimate the prevalence of athlete burnoutbased on clinical cut-off scores taken from the Shirom Melamed Burnout Questionnaire (SMBQ). Todo so, cut-off scores were converted from the SMBQ to the Athlete Burnout Questionnaire (ABQ).This provided a cut-off score of 3.14. Data were derived from one cross-sectional sample (N = 1,931)and one 10-week longitudinal sample (N = 186; 10 waves). Analyses focused on the physical andemotional exhaustion subscale of the ABQ. In the longitudinal sample, the stability of the cut-offswas examined (i.e., those athletes scoring over 3.14 for over 50% of the time-points, versus thosewho never scored above 3.14). For the cross-sectional sample, 13% of athletes scored above theclinical cut-off score. For the longitudinal sample, 7.1% of athletes scored above the cut-off on over50% of occasions, while 77.6% of athletes never scored above the cut-off score on any occasion. Thepresent findings suggest that the estimated prevalence of athlete burnout differs when crosssectional data are analysed than when longitudinal data are utilised. The findings reiterate that asignificant proportion of athletes are at risk of burnout and that prevalence seem to be similarcomparing with student- and working populations.