Background No research has assessed Hamilton Rating Scale for Anxiety (HRSA) psychometric properties in Ethiopian university students, using item response theory (IRT) and classical theory.Aims This study aimed to assess psychometric properties of the English HRSA in Ethiopian students, using IRT and classical theory.Method University students (N = 370, age 21.44 +/- 2.30 years) in Ethiopia participated in a cross-sectional study. Participants completed a self-reported measure of anxiety, a sociodemographics tool and interviewer-administered HRSA.Results Confirmatory factor analysis (CFA) favoured a one-factor structure because fit indices for the one-factor model; and two distinct two-factor models were similar, but high interfactor correlations violated discriminant validity criteria in two-factor models. This one-factor structure showed structural invariance as evidenced by multi-group CFA across gender groups. No ceiling/floor effects were seen for the HRSA total scores. Infit and outfit mean square values for all the items were within the acceptable range (0.6-1.4). Four threshold estimates (tau i1, tau i2, tau i3 and tau i4) for each item were ordered as expected. Differential item functions showed item-level measurement invariance for all the 14 HRSA items across gender for both uniform and non-uniform estimates. McDonald's omega and Cronbach's alpha for the HRSA tool were both 0.88. The convergent validity of the interviewer-administered HRSA with self-reported anxiety subscale of the 21-item Depression, Anxiety and Stress Scale was weak to moderate.Conclusions The findings favour the validity of a one-factor structure of the HRSA with adequate item properties (classical and rating scale model), convergent validity, reliability and measurement invariance (structural and item level) across gender groups in Ethiopian university students.