Research has shown that witnessing partner violence (WPV) increases the likelihood of experiencing or perpetrating violence in later romantic relationships, but little is known about the mechanisms underlying this process. This study examines the relationships between preference for unsuitable partners and teen dating violence (TDV) among adolescents who have witnessed parental violence or not. Attachment was also considered. Participants were 356 adolescents, both witnesses and non-witnesses of partner violence. Results showed no difference in preferences (for good, risky, or loving partners) between the two groups. However, preference for unsuitable partners did significantly predict TDV perpetration and victimization, but only among witnesses. Also, loving-partner preference moderates the relationship between WPV and TDV perpetration among highly avoidant witnesses. Findings indicate a new avenue for prevention through targeting partner preferences.