The literature proposes that leisure boredom may systematically increase during adolescence. Moreover, some authors assume that this hypothesized developmental trend is associated with increases in youthful delinquency and depression. Individual dispositions (e.g., temperamental disinhibition) are believed to exacerbate the relationship between boredom and delinquency. This study investigated whether (1) leisure boredom really is an increasing phenomenon during early adolescence; (2) gender, temperamental disinhibition, shyness, family relationship quality, peer rejection, a deprived school context, and rural/urban living explain developmental variations in boredom; (3) boredom is longitudinally and reciprocally related to delinquency and depression; and (4) bored disinhibited adolescents are particularly likely to become delinquent and to use delinquent acts to mitigate boredom. Analyses were based on a German sample of school students (N = 722) who provided annual self-reports on study variables from age 10 to 14 years. Bivariate growth curve models captured correlations between developmental trajectories of boredom and delinquency/depression. Cross-lagged models examined reciprocal short-term associations. Analyses revealed a modest increase in leisure boredom during early adolescence. Disinhibition and qualities of proximal social contexts (family, peers, school) were related to boredom with peer rejection showing the most consistent longitudinal association. Boredom was developmentally associated with depression whereas longitudinal associations with delinquency were weaker and more short-term. Temperamentally disinhibited adolescents appeared to buffer leisure boredom by means of delinquency. Results support person-context models of leisure boredom with regard to its etiology and consequences. Findings further demonstrate that leisure boredom plays a prominent role in the developmental adaptation of adolescents.