Adaptation to imprisonment involves feelings of safety, autonomy, well-being, stress or misbehaviour among detained offenders. According to importation theory, characteristics such as previous experiences of imprisonment or psychiatric problems affect the adaptation of offenders to imprisonment; deprivation theory, in contrast, focuses on factors such as social interactions with peers or staff and fairness in procedures or in daily life encounters. In this study, adaptation to imprisonment and the relationship with importation and deprivation factors were investigated among 207 juvenile offenders incarcerated in Dutch juvenile correctional institutions. A cross -sectional multi-method design was used, including a survey, screening instruments, records and qualitative interviews. Controlling for importation characteristics, strong associations of adaptation to imprisonment were found with interactions with peers and staff, justice, daily activities and the number of juveniles in a group. The study provides valuable insight into the factors related to adaptation to imprisonment, which can help to improve safety in prison and, subsequently, could be useful in increasing the motivation of juveniles to participate in treatment programmes. The implications for theory and practice are discussed.