Studies of gambling starting before adulthood in the general population are either cross-sectional, based on the stability of these behaviors between 2 time points, or cover a short developmental period. The present study aimed at investigating the developmental trajectories of gambling problems across 3 key periods of development, mid-adolescence, early adulthood, and age 30, in a mixed-gender cohort from the general population. Using a semiparametric mixture model, trajectories were computed based on self-reports collected at ages 15 (N = 1,882), 22 (N = 1,785), and 30 (N = 1,358). Two distinct trajectories were identified: 1 trajectory including males and females who were unlikely to have experienced gambling problems across the 15-year period, and 1 trajectory including participants likely to have experienced at least 1 problem over the last 12 months at each time of assessment. Participants following a high trajectory were predominantly male, participated frequently in 3 to 4 different gambling activities, and were more likely to report substance use and problems related to their alcohol and drug consumption at age 30. Thus, gambling problems in the general population are already observable at age 15 in a small group of individuals, who maintain some level of these problems through early adulthood, before moderately but significantly desisting by age 30, while also experiencing other addictive behaviors and related problems.