The aim of this study was to analyze associations between demographic factors, family psychosocial characteristics, tobacco, alcohol, and other drug use, and adolescent motherhood. This was a case-control study in Porto Alegre, Rio Grande do Sul State, Brazil, with 431 adolescents 14 to 16 years of age who gave birth in 2009 (cases) and 862 adolescents who had never given birth (controls). Three-stage hierarchical logistic regression was performed (demographic, family psychosocial, and lifestyle variables). Lower economic class, not having lived with the parents from 10 to 14 years of age (OR = 1.67; 95%CI: 1.12-2.48), having taken care of other children (OR = 1.42; 95%CI: 1.09-1.87), siblings who had children before 20 years of age (OR = 1.56; 95%CI: 1.192.06), having tried smoking (OR = 1.94; 95%CI: 1.35-2.78), and having arrived home intoxicated (OR = 1.67; 95%CI: 1.12-2.48) were associated with adolescent motherhood. Greater attention should be given to family relations in association with tobacco and alcohol consumption, since the use of these substances is associated with adolescent motherhood.