Intimate partner violence (IPV) among homeless youth (HY) is common, yet it has continuously been understudied, especially in relation to substance use. As part of a longitudinal study of Los Angeles area HY, drop-in service seeking youth completed a self-administered questionnaire. The presented results are from the third panel of data collection (N = 238), and the Revised Conflict Tactics Scale (CTS2) was used to assess IPV behavior regarding the participant’s most recent intimate relationship. Approximately 38% of participants reported IPV behavior in their most recent relationship, and the majority of this behavior was bidirectional. It was unlikely that a HY was only a victim or only a perpetrator. Multivariable models revealed that bidirectional IPV was related to increased odds of recent methamphetamine; whereas sole perpetration was associated with an increased likelihood of ecstasy use. Specific substance use and IPV are closely related to risk behaviors for HY. Comprehensive interventions should be developed to address both these risk behaviors.