Various Dutch secure residential youth care (SRYC) institutions are implementing a family-centered approach aiming to increase parental involvement and improve treatment outcomes. However, it remains unclear if and how family-centeredness (FC) is related to increased parental involvement and to improved treatment outcomes of adolescents. In this study, we unravelled the relation between FC, parental involvement, and behaviour problems of adolescents in SRYC. Families of 404 adolescents admitted to one of seven participating Dutch SRYC institutions completed a survey (at the start, at the end, and at 6-months follow-up) on problem behaviour of adolescents. In addition, 411 group care workers filled out a questionnaire about their residential group’s level of FC every 6 months. Moreover, the mentor of each adolescent filled out a questionnaire about the level of parental involvement. We analysed the data using multiple mediator models. Associations were found between FC and parental involvement. However, no relation was found between FC and adolescent problem behaviour, and no mediation and no moderation effects of parental involvement were found. Overall, results showed that most parents were involved during the residential stay, and, independent of FC, adolescent problem behaviour decreased over time. Implementing FC in SRYC institutions seems to be helpful in involving parents during the residential stay, but was not found to be associated with adolescent behavioural outcomes. Our results indicate that institutions could improve their level of FC by offering more informal contact moments for parents and by addressing barriers to FC among residential staff.