Objective: Maternal attention-deficit/hyperactivity disorder has not been investigated in relation to parenting skills in adolescent mothers. This study investigated whether maternal inattention and hyperactivity/impulsivity symptoms early in pregnancy predict poorer parenting skills and infant maltreatment during the first year of life in adolescent mothers living in adverse environmental conditions. Methods: The participants in this study were 80 adolescent mothers aged 14-19 years and their babies who were taking part in a randomized controlled trial on the effects of a home-visiting program on infant development. Symptoms of maternal attention-deficit/hyperactivity disorder were assessed in the first trimester of pregnancy. Parenting skills (maternal competence, attachment to the baby, home environment) and child maltreatment were assessed when the infants were aged 6 and 12 months. Multilevel linear regression models were constructed to test the extent to which prenatal maternal inattention and hyperactivity/impulsivity symptoms predicted these parenting variables during the first year of the infant’s life. Results: Prenatal inattention symptoms significantly predicted lower maternal competence and attachment, a poorer home environment, and greater maltreatment during the first year of life. Hyperactivity did not significantly predict parenting skills or maltreatment. Conclusions: Our findings suggest that inattention symptoms may interfere with parenting abilities in adolescent mothers and should be considered in early intervention programs.