Research on adults generally focuses on secrecy’s physical and psychological disadvantages for the secret-keeper, based on traditional attitudes that secrecy is problematic. The current study proposed that secrecy might have developmental functions with particular importance during adolescence. The participants included 110 students ages 12-13 years in 7th grade and 117 students ages 16-18 years in 11th and 12th grades. The students attended two schools in the Netherlands that provided classes covering both age groups. Participants completed questionnaires that collected information abut secrecy from parents, physical symptoms, depressive mood, loneliness, emotional autonomy, disclosure toward parents, quality of the relationship with parents, and frequency of contact with friends and peers. Results revealed that keeping secrets from parents related to physical and psychological disadvantages in adolescence. However, results also revealed that secrecy related to adolescents’ emotional autonomy. The analysis concludes that secrecy is a powerful mechanism in adolescent well-being and psychosocial development and is also a complex but unique concept that deserves research attention, especially in relation to adolescence. Tables and 65 references