As availability of parent-child interaction curricula increases, Early Head Start (EHS) provides a relevant context to test research-based parenting models as part of everyday practice. We trained EHS staff to incorporate the Promoting First Relationships (PFR) intervention into ongoing weekly home visits with mothers and their young children (n = 102) enrolled in EHS. Children had a mean age of 19.75 months and were 56% Hispanic, 23% Black, and 14% White. Families were randomly assigned to an intervention group where they participated in PFR as an EHS enhancement, or to a waitlist-control group where they received only typical EHS services. To explore the possibility that effectiveness of parent-child curricula may differ based on child characteristics, we used linear regression to examine children's temperament as a potential moderator of PFR efficacy on outcomes related to parenting stress, family functioning, and parent-child interaction. While we did not find a significant main effect of PFR for the full sample, there were several significant moderated effects. For families where children showed higher levels of surgency, mothers' parenting stress was significantly reduced after PFR participation. Also, when children showed higher levels of negative affect, mothers demonstrated higher sensitivity in parent-child interactions after participating in PFR. Given findings from our exploratory study, agencies should consider the characteristics of families served and the match with intervention priorities, when selecting intervention programs. When delivered as a home visitation enhancement, PFR may be a valuable support for certain enrolled families, based on child characteristics including high levels of surgency or negative affect.