The aims of the present study were: (1) identify and compare the biological maturity in Portuguese gymnasts across competitive levels; (2) investigate how morphological variables and training volume behave in the different status and indicators of maturity and (3) determinate if the maturity status influences the competitive performance. The sample (n=164) consisted of three competition levels (Base, 1st division and Elite) from Portugal. Anthropometric measurements and body composition were performed. For analysis of biological maturation, the sexual and somatic maturation were evaluated. For the statistical analysis, Mann-Whitney and Kruskal-Wallis tests, Pearson correlation and Linear Regression were used. In total, 63.4% of gymnasts had not yet reached menarche and the higher competition level, lower the number of gymnasts with menarche. On mean, all groups had reached the age at peak height velocity. The higher the competition level, higher the chronological age and age at peak height velocity. Thus, the maturation indicators showed a delay in pubertal development in all competition levels and the elite gymnasts seem present a later pubertal development. The chronological age, the values of body mass, height, BMI and body fat increased with the maturity status according all maturity indicators. However, gymnasts with different maturity status revealed similar training volume. Finally, the maturational status explained 11.5% of competition success with higher advantage in the competitive performance to prepubertal gymnasts. Thus, the premenarcheal status and a higher age at peak height velocity contribute to performance in Rhythmic Gymnastics.