BackgroundThe transition period after psychiatric hospitalization back to school is accompanied by various challenges, including a substantial risk for rehospitalization. Self-efficacy and self-control, as transdiagnostic variables and important predictors of coping with school demands, should be crucial factors for successful adaptation processes as well as an overall high well-being during school reentry. The present study therefore investigates how patients’ well-being develops during this period, and how it is related to patients’ self-control and academic self-efficacy, as well as parents’ and teachers’ self-efficacy in dealing with the patient.MethodsIn an intensive longitudinal design, daily ambulatory assessment measures via smartphone were collected with self-reports from the triadic perspective of 25 patients (Mage= 10.58 years), 24 parents, and 20 teachers on 50 consecutive school days, starting 2 weeks before discharge from a psychiatric day hospital (mean compliance rate: 71% for patients, 72% for parents and 43% for teachers). Patients answered daily questions between five and nine o'clock in the evening about their well-being, self-control, academic self-efficacy and about positive and negative events at school, as well as parents and teachers about their self-efficacy in dealing with the patient.ResultsMultilevel modeling revealed that on average, patients’ well-being and self-control decreased during the transition period, with trends over time differing significantly between patients. While patients’ academic self-efficacy did not systematically decrease over time, it did show considerable intra-individual fluctuation. Importantly, patients experienced higher well-being on days with higher self-control and academic self-efficacy as well as with higher parental self-efficacy. Daily teacher self-efficacy did not show a significant within-person relationship to daily patients’ well-being.ConclusionsWell-being in the transition period is related to self-control and self-efficacy of patients and their parents. Thus, addressing patients’ self-control and academic self-efficacy, as well as parental self-efficacy, seems promising to enhance and stabilize well-being of patients during transition after psychiatric hospitalization.Trial registrationNot applicable, as no health care intervention was conducted.Supplementary InformationThe online version contains supplementary material available at 10.1186/s40359-023-01197-0.