Peer influence is a well-studied and established phenomenon in the social sciences with much research focusing on peers influencing one another in negative ways. However, peers have also been shown to provide a positive influence. Research on substance treatment programs indicates that one's social network can influence one to enter treatment as well as help maintain abstinence following the completion of the program. However, little is known about the influence that peer's drug treatment can have on the substance levels of an individual. I use the peer nomination data and Waves 1 and 2 of the National Longitudinal Study of Adolescent to Adult Health to study this instance of peer influence. Results indicate that having a higher proportion of peers who attend drug treatment is not associated with lower levels of respondent illicit drug, alcohol use, and binge drinking behaviors. Consistent with past findings, having a higher proportion of one's peers who reported drug use is associated with higher levels of respondent substance use. Implications for clinicians and other treatment providers are discussed with an emphasis on the role that strong parental attachment can play in offsetting negative peer influence.