Most studies of parents in drug treatment have focused exclusively on mothers, and few studies have examined the effects of parents' level of involvement with their children on the parents' drug use and psychological functioning, either before or after treatment. This study examined mothers and fathers (n = 331) who were parents of children under the age of 18; participants were sampled from 19 drug treatment programs across four types of treatment modalities in Los Angeles County. A majority of each group (57% of 214 mothers and 51% of 117 fathers) were classified as being highly involved with their children. At the baseline assessment, higher parental involvement was related to lower levels of addiction severity, psychological severity, and symptoms of psychological distress, and to higher levels of self-esteem and perception of parenting skills. In general, fathers had higher levels of alcohol and drug-use severity than did mothers, but fathers who were more involved with their children showed lower levels of addiction severity than fathers who were less involved. Parental involvement at baseline was unrelated to drug use at the 12-month follow-up, although parents who were less involved with their children reported experiencing more stressors. Given the association of parental involvement with lower levels of addiction severity and psychological distress at baseline, treatment protocols should build upon the positive relationships of parents with their children, and seek to improve those of less-involved parents.