The purpose of the study was to explore the effect of maturation on the body size–physical performance relationship. Based on our previous study that evaluated only muscle strength (16), we hypothesized that the physical performance tested on pubescent subjects would be related to body size at a higher rate than predicted by standard scaling theory applied on pre- and postpubescent subjects. Six age groups of highly selected and trained junior soccer players (N = 478; age 12–17 years) presumably including prepubescent, pubescent, and postpubescent subjects were evaluated. They were tested using various standard tests of maximum physical performance including muscle strength of 3 leg muscle groups, 2 jumps, sit-ups, hand and foot tapping, and agility. The results revealed a steeper increase of the tested performance with an increase in body size for the pubescent age than for the pre- and postpubescent age. The observed phenomenon was interpreted by different level of maturation of the subjects tested within the same pubescent age group. We conclude that maturation alters the effect of body size on various physical performances and, therefore, this phenomenon needs to be taken into account when interpreting the data from the physical performance tests applied on pubescent subjects.