The aim of the present study was to verify the relative age effect (EIR) in athletes of the Brazilian Basketball Championship Under-17, considering the gender and final classification of the team in the championship. Thus, 540 basketball players (270 of each sex) were grouped in quartiles, according to the month of birth. To compare them by the classification obtained, the players were grouped in: “Medalists”, “Intermediates” and “Last placed”. All information pertinent to the study was obtained through the website of the Brazilian Basketball Confederation. The chisquare test (χ2) was used to analyze the data. From the results obtained, there was a predominance of athletes born in the 1st and 2nd quartiles (χ2 = 23.78; p <0.001), with the highest RIR in males (χ2 = 16.74; p <0.001) when compared to females χ2 = 8.45, p=0.038). In relation to the final classification of the championship, the effect was found in male “medalists” (χ2 = 8.28, p=0.041) and female players (χ2 = 9.43, p=0.024) and in the “intermediate” male players (χ2 = 13.08, p=0.004).