Background: In order to facilitate people with psychosis to increase their physical activity (PA) levels, a reliable measure- ment of these levels is of relevance. Objectives: The primary aim of current study was to explore the test-retest of the Simple Physical Activity Questionnaire (SIMPAQ) in Ugandan outpatients with psychosis. A second aim was to explore correlates of the SIMPAQ, including de- mographic variables and antipsychotic medication dose. Methods: Thirty-four women (33.9±8.0 years) and 21 men completed the SIMPAQ twice in a day. The test-retest reliability was assessed using Spearman Rho correlations coefficients. Differences in subgroups were analysed with Mann Whitney U tests. Results: The SIMPAQ showed a good test-retest reliability with correlates ranging from 0.78 (P<0.001) for structured exer- cise to 0.96 (P<0.001) for walking. Women, non-smokers and those without HIV/AIDS showed higher incidental PA than men, smokers and those with HIV/AIDS. Conclusion: The SIMPAQ is a reliable tool to assess PA and sedentary levels in Ugandan outpatients with psychosis. Men, smokers and those with HIV/AIDS appear to be at risk for lower incidental PA. Keywords: Physical activity; sedentary lifestyle; psychosis.