Child maltreatment (CM) is a common condition with a large impact on the victim and society. In the Netherlands, the preventive child healthcare (CHC) aims to protect children against such threats. However, several studies indicate that the efficacy in this area may be suboptimal for many CHC professionals. Therefore, this study aims to map the practice variation in the primary and secondary prevention of CM, by CHC physicians and –nurses. This mixed-methods study used interviews to identify relevant topics and develop an online questionnaire. All CHC organizations in the Netherlands (n=45) were asked to forward this questionnaire to their professionals. Practice variation was described with domain scores and item response distributions. Multi-level analysis was used to assess casemix-corrected variance between organizations. Interview participants (n=11) expected suboptimal care in 35 topics which they considered important for prevention of CM, resulting in a 15 minute questionnaire. Nearly two-thirds of the organizations (n=29) agreed to forward the questionnaire to their employees. The response rate was 42% (n=1104). Suboptimal care and practice variation was found in all domains (i.e. communication, medical expertise, collaboration, involvement in prevention of CMactivity, and improvement opportunities), mostly caused by intra-organization variance. Significant inter-organization variance was found for collaboration (variance partition coefficient 6-7%) and involvement activity (2-3%). Furthermore, the majority of the respondents (96%) reported fear in acting upon suspicions of CM. Substantial suboptimal care and practice variation in prevention of CM warrant action from authorities, CHC training institutes, CHC organizations, and professionals.