Parental involvement in youth sports is increasingly relevant in scientific research since parents have gradually developed awareness regarding youngsters' sports experiences. This study aimed to (1) examine potential differences in athletes' and parents' perceptions of parental involvement practices in youth basketball, (2) verify whether these perceptions differ by sex, and (3) analyze the relationship between the different perceptions dimensions recorded. The analysis included a large sample of 423 Portuguese participants (151 youth basketball athletes and 272 parents) who completed the Parental Behaviors in Sports (PBSP) questionnaire. The PBSP comprises a version for parents and a version for athletes, composed of five dimensions: (1) sports support, (2) competition attendance, (3) technical influence, (4) performance pressure, and (5) sports expectations. No significant statistical differences regarding PBSP dimensions were observed between boys and girls in the athletes' group. However, in the parents' group, fathers scored significantly lower than mothers in sports expectations (p = 0.001). Differences between athletes' and parents' perceptions were evident in competition attendance (p = 0.023), technical influence (p ≤ 0.001), and sports expectations (p = 0.023). When analyzing the dyads of boys-fathers and girls-mothers, significant differences were found for technical influence (p = 0.035), performance pressure (p = 0.020), and sports expectations (p < 0.001) between boys and fathers. Among girls and mothers, differences were perceived exclusively for technical influence (p = 0.005). Finally, technical influence correlated significantly with performance pressure (r = 0.351, p < 0.001) and sports expectations (r = 0.367, p < 0.001). These findings demonstrate the crucial importance for sports researchers and practitioners to consider differences in perceptions based on sex and role (athlete or parent) when designing and implementing parental educational programs.