Purpose Initiation of marijuana during adolescence is associated with negative outcomes and is more common among those with criminal justice involvement. We sought to determine demographics, psychosocial factors, mental health factors, and criminal outcomes associated with earlier age at first marijuana use in a criminal justice population. Methods Data from structured, in-person interviews of adults in a criminal corrections program were analyzed. Participants (689 men and women ages 19 and older) were recruited for a larger smoking cessation trial (2009–2013) as a volunteer sample by flyers at a community corrections site. 516 had smoked both nicotine and marijuana and were included in the analysis. We determined associations between self-reported age at first marijuana use and sex, race, income, educational attainment, history of abuse, family problems, psychiatric problems, criminal record, and age of nicotine and alcohol initiation. Results Of 516 participants, 68% were men, and 64.5% were Black. No participants were of Hispanic ethnicity. Average age of marijuana initiation was 15.1 years (SD 3.7 years). After linear regression, earlier age at marijuana initiation was associated with male sex and more criminal offenses (person/violent and court). Race and psychiatric problems were not associated with earlier marijuana initiation. Conclusions Earlier adolescent marijuana initiation is associated with more criminal offenses in a criminal justice population. Men initiate marijuana earlier than women. Adolescents at high risk of justice involvement may benefit from delayed initiation of marijuana, specifically men. Additional studies should examine prevention strategies for adolescent marijuana use that target those at highest risk.