OBJECTIVES: This paper outlines the development and initial pilot of the Sibling Sexual Behaviour Mapping Tool (SSBMT). Building on the findings of the National Project on Sibling Sexual Abuse (King-Hill, McCartan, et al., 2023) and work by Yates and Allardyce (2023), the tool was devised with the aim of supporting frontline child-protection social workers during the initial stages of working with families where sibling sexual behaviours (SSB) may be present. METHODS: This paper explores the rationale for the SSBMT design, and preliminary findings from the first phase of resource evaluation. The evaluation process comprised a small pilot with social workers across seven local authorities in the United Kingdom (UK). The pilot study sought to assess the workability and effectiveness of the SSBMT within social work practice, providing stakeholder insight prior to its launch. The study employed mixed methods to gain feedback on the SSBMT design, accessibility, ease of use and compatibility with current child protection work processes, which included training of 50 practitioners, surveys with 20 professionals and two semi-structured interviews. FINDINGS: The findings suggest that the SSBMT increased practitioner confidence when working with SSB, and promoted holistic, whole-family approaches in the initial stages of work with children and families affected by SSB.