Parental reflective functioning (PRF) is considered a key parental competence. Since most research on PRF has focused on infancy or the first years of life, there is a gap in our understanding of PRF among parents of older children. Therefore, we investigated PRF in mothers and fathers with preschool-aged children, examining associations between PRF, parent's romantic attachment, and observed parenting behavior. The sample comprised 50 mothers, 40 fathers, and their 5-year-old children. PRF was assessed using the parental reflective functioning questionnaire (PRFQ), parental romantic attachment was assessed using the experiences in close relationships scale-revised (ECR-R), and parenting behavior was assessed during a parent–child free-play interaction with the coding interactive behavior (CIB) coding system. Results showed that mothers scored higher on the interest and curiosity scale than fathers, indicating that mothers show a more active interest and curiosity in their child's mental states. Further, higher levels of attachment anxiety in fathers were associated with higher levels of pre-mentalizing modes. In mothers, higher levels of attachment avoidance were associated with lower levels of interest and curiosity. Finally, and unexpectedly, higher levels of interest and curiosity in mothers were associated with less sensitivity during free play. In summary, the study found meaningful associations between mothers' and fathers' romantic attachment and their PRF indicating a spill-over of their attachment strategies into their relationship with their child. Further, the study results suggest that very high levels of interest and curiosity in mothers reflect hypermentalizing.