With the increasing prevalence of mental health difficulties in sport, athletes may be at greater risk of burnout than ever before. In the present study, we tested this possibility by examining whether average athlete burnout levels have changed over the past 2 decades, from 1997 to 2019. A literature search returned 91 studies ( N = 21,012) and 396 effect sizes. Findings from cross-temporal meta-analysis suggested that burnout symptoms have increased over the past 2 decades. Specifically, we found that athletes’ mean levels of reduced sense of athletic accomplishment and sport devaluation have increased. As burnout symptoms are now typically higher among athletes than in the past, we can expect more athletes to be prone to the negative effects of burnout. Sport is therefore in urgent need of prevention and intervention strategies to stop and reverse this trend.