One particular developmental task during adolescence is to regulate fluctuating moods to successfully transition through this period. The aim of this person-centered study was to identify distinct developmental trajectories of adolescent mood variability and to compare adolescents in different trajectories on changes in depressive symptoms, delinquency, and alcohol consumption in early to middle (ages 13-16) and middle to late adolescence (ages 16-20). Dutch adolescents (n = 482, 57.1% male) rated their daily emotions three weeks per year for five years using Internet daily diaries (ages 13-18). Day-to-day mood changes were calculated as an indicator of mood variability. Adolescents provided annual reports on depressive symptoms, delinquent acts, and alcohol consumption (ages 13-20). Results showed that most adolescents (88%) followed a trajectory characterized by decreases in mood variability (i.e., more stable moods). However, a minority (12%) followed a trajectory of increases in mood variability with a peak during middle adolescence. Adolescents with an increasing mood variability trajectory showed stable depressive and delinquency symptoms in early to middle adolescence compared with adolescents with a decreasing mood variability trajectory, who showed a decline in these symptoms. At age 16, there was a significant difference between the groups in depressive and delinquency symptoms, which stayed stable toward late adolescence. Although the two groups did not differ concerning alcohol consumption in early to middle adolescence, adolescents from the increasing mood variability class experienced less steep increases in alcohol use from middle to late adolescence compared with adolescents from the decreasing mood variability class.