Abstract Background Among the few existing needs assessment tools for family carers, the 14-item Carer Support Needs Assessment Tool (CSNAT) is the only brief and holistic needs screening tool designed for everyday use in palliative care practices. The aim of this study was to evaluate the reliability, validity, and acceptability of the traditional Chinese version of the CSNAT in palliative care settings in Hong Kong. Methods This adopted a cross-sectional and correlation design with repeated measures. The participants were 125 family carers of palliative cancer patients and 10 healthcare providers (HCPs) that were recruited from two local hospitals. The evaluation of psychometric properties included the following: (1) content validity through HCPs including frontline physicians, nurses, social workers, and clinical psychologists; (2) construct validity between the CSNAT items and those of the validated tools that measured caregiver burden, social support, and caregiving self-efficacy; and (3) one-week test-retest reliability in a sub-sample of 81 caregivers. The acceptability of the tool was assessed by the carers using several closed-ended questions. Results The content validity index of the CSNAT at the scale level was 0.98. Each item of the CSNAT was significantly and moderately correlated with caregiver burden (Spearman’s r = 0.24 to 0.50) and caregiving self-efficacy (r = − 0.21 to − 0.52), but not for social support. All CSNAT items had fair to moderate test-retest reliability (weighted kappa = 0.21 to 0.48), with the exception of two items “managing your relatives’ symptoms, including giving medicines” and “having time for yourself in the day”. Regarding the acceptability of the CSNAT, almost all HCPs were willing to use the CSNAT for carer assessment and support. 89.6% of the carers demonstrated a comprehensibility of the CSNAT tool and 92.9% felt comfortable answering the questions. Around 90% of the carers agreed to use the tool for screening, discussing needs, and making referrals. Conclusion The traditional Chinese version of the CSNAT is a tool with high validity and acceptability and adequate reliability that measures family carers’ support needs, which should be considered for wide application in local palliative care practices.