Annual age grouping of children according to their birth year is a common practice of the educational systems of many countries. This variation in birth dates among children grouped in the same generation is known as relative age and its implications on different developmental outcomes are referred to as relative age effects (RAEs). The previous body of research of RAEs in youth populations has focused on sporting samples; however, studies examining RAEs in physical education are scarce. The current study investigates the influence of the RAEs on motor abilities in a sample of adolescent pupils. The results indicate significant differences in motor abilities between relatively older and relatively younger participants of both sexes. Since RAE is an under-researched area in physical education, the results may have substantial implications for PE assessment given the fact that many PE teachers still carry out typical norm-referenced assessments. Possible recommendations for future research are discussed.