Background <p>The Health and Social Care Professionals’ Knowledge and Attitudes towards Later-Life Intimacy and Sexuality (HSCP-KALLIS) is designed to assess health and social care professionals’ knowledge and attitudes toward later-life intimacy and sexuality. Additional care considerations are included for older adults with dementia and those from diverse gender backgrounds. This study aimed to evaluate the reliability and validity of the HSCP-KALLIS scale.</p> Methods <p>This methodological study was a subsequent phase of the HSCP-KALLIS scale development undertaken between 2022 and 2023, using an online survey approach with participants who were health and social care professionals. Internal consistency was assessed using McDonald’s Omega and Cronbach’s alpha, while the underlying factor structure of the scale was examined through exploratory factor analysis.</p> Results <p>A total of 98 participants were recruited for the study. Participants primarily were females, registered nurses, worked in aged care, and demonstrated high levels of knowledge and positive attitudes towards later-life intimacy and sexuality. The final HSCP-KALLIS Scale consists of 30 knowledge items across two factors and 25 attitude items across three factors, with satisfactory internal consistency demonstrated.</p> Conclusions <p>This study provides preliminary evidence that the HSCP-KALLIS scale is a reliable tool for measuring health and social care professionals’ knowledge and attitudes towards later-life intimacy and sexuality. This scale shows potential for identifying staff training needs, evaluating training effectiveness, and informing policy and guidelines development. The primary study limitations include methodological constraints and a small sample size. Future research should involve a larger sample size to enable confirmatory factor analysis.</p> Trial registration <p>Not applicable.</p>