Prioritized attention to faces can be viewed as an early-developing marker of social engagement. This behavior is closely linked with early interactions, but there has been little research examining the longitudinal associations between social engagement and parent–child interaction. We examined the reciprocal relations between mother–child interaction and child engagement with faces from infancy to preschool age. Participants of this study were 738 mother–child dyads from the FinnBrain Birth Cohort. We used Emotional Availability Scales to examine mothers’ emotional availability in interaction and eye tracking to examine attention dwell time for pictured faces and nonface patterns under distraction at 8, 30, and 60 months. Using a random intercept cross-lagged panel model, which differentiates between-dyad variance from within-dyad variance (deviations from the individual’s latent average), we found that higher maternal emotional availability was associated with shorter dwell time for faces at the between-dyad level. At the within-dyad level, stability (smaller deviations from the individual’s latent average) in a mother’s emotional availability at 30 months was associated with stability in the child’s face engagement in the subsequent assessment at 60 months. Similar associations were not found in analyses of dwell times for nonfaces. Together, our findings show an interconnection between mother–child interaction and the child’s engagement with faces and raise the possibility that shifts in the quality of these interactions within specific developmental stage may lead to changes in how children engage with social cues. (PsycInfo Database Record (c) 2024 APA, all rights reserved)