The Parental Reflective Functioning Questionnaire (PRFQ; Luyten et al., 2017) is a central measure of parental reflective functioning (i.e., the tendency to consider children's mental experiences); still, little is known about the psychometric properties of the PRFQ among maltreating and nonmaltreating mothers. Maltreating mothers may have difficulties with parental reflective functioning given their risk for biased child-related cognitions and difficulties with sensitive emotion socialization. The present study investigated measurement invariance and the concurrent validity of the PRFQ in a sample of racially diverse, low-income maltreating (n = 165) and nonmaltreating (n = 83) mothers of preschoolers. Mothers were enrolled in a randomized controlled trial of a brief intervention (Valentino et al., 2019). A three-factor model emerged, representing the subscales (prementalization, certainty about mental states, and interest and curiosity) identified in a previous validation study of the PRFQ (Luyten et al., 2017); however, three items were excluded due to low factor loadings. Scalar group-based (maltreating vs. nonmaltreating) and longitudinal measurement invariance was found. Maternal prementalization and interest and curiosity were associated with emotion socialization behavior.