The present reserch focuses on studying the perception of motor self-competence in young girls. It also deals with the possible relationship of self-perception with the physical condition they have. Based on the results obtained, it can be affirmed that boys have a better perception of their competence than girls but in general most young people (in all cases more than 49%) perceive themselves to be fairly competent. The physical condition shows objective values resulting from the physical tests. In absolute terms, boys between 12 and 15 years old are faster and stronger than girls, and at the same age, girls are more stretch. Differences in physical condition can be explained by biophysiological issues. Finally, by relating the self-perception that young people have of their motor competence and their physical condition, it is clear that, in absolute terms, those who perceive themselves to be less competent are those who have less conditional capacity.