Aim To develop and psychometrically evaluate the Family and Staff Relationship Attitude Tool (FASRAT) for use in Australian residential aged care facilities to assess the attitudinal beliefs of residential aged care staff towards staff–family relationships. Methods Development and testing of the psychometric properties of the 26‐item FASRAT occurred in three phases which included item development based on a systematic review of the research literature, interviews with aged care staff and families, expert panel review and testing with aged care staff. Results Content validity and internal consistency of the FASRAT support its use as an instrument to measure staff attitudinal beliefs about staff–family relationships in the residential aged care setting. Conclusion The FASRAT will enable residential aged care facilities to measure the attitudinal beliefs of its staff about staff–family relationships and provide a basis for the development and implementation of interventions to address identified gaps which impact on relationship quality.