Prevention services can promote public health by building protective factors and reducing maltreatment risk. Yet, engaging caregivers in prevention services presents a unique set of challenges. Measurement studies are important first steps to increase the knowledge of caregiver engagement in prevention services. The purpose of this scoping review was to investigate how family engagement has been measured and operationalized in the studies of maltreatment prevention/positive parenting programs. The review examined quantitative and mixed methods studies conducted in the U.S., which measured multiple dimensions of client engagement, including behavioral, attitudinal, and relational domains. A total of 88 studies selected from PubMed, CINAHL, ERIC, PsycINFO, Social Work Abstracts, Academic Search Premier, and Web of Science were included in this review. Results indicated that studies examine engagement constructs in all three domains of engagement with a primary focus on behavioral engagement. The attitudinal and relational engagement was mostly assessed through general satisfaction surveys, and a limited number of studies utilized validated measures to assess those constructs. While most studies reported acceptable internal reliabilities, only two studies reported other dimensions of psychometric qualities. Only one validated measure was found, which assessed client perceptions of provider cultural competence. More measurement studies are needed to further incorporate multiple dimensions of engagement into the studies of maltreatment prevention programs, which can inform the effort to develop tailored implementation strategies to fully engage various groups of parents in maltreatment prevention programs.