BACKGROUND: People seeking care at primary healthcare centres may be exposed to work-related stress, increasing the risk of future sick leave. Thus, it is important to identify work-related stress, and to explore how stress relates to work ability and health. OBJECTIVE: To investigate the association between work-related stress and a) work ability, and b) self-rated health, among working women and men seeking care for physical or mental health complaints. METHODS: This cross-sectional study analyzed baseline data (n = 232) from a randomized controlled trial investigating the effects of a brief intervention to prevent sick leave. Data regarding work-related stress, work ability and self-rated health were analyzed using binary logistic regression models. RESULTS: In models adjusted for age, gender and education, high work-related stress measured by the Work Stress Questionnaire was significantly associated with low work ability. The highest odds ratio (OR 3.27, 95% CI 1.66–6.42) was found between the domain “interference between work and leisure time” and work ability, suggesting a more than three times higher odds for low work ability when perceiving that work interferes with leisure time. No significant association was found between work-related stress and self-rated health. CONCLUSION: Health professionals should explore patients’ work-related stress when they seek care for physical or mental complaints in primary healthcare. Patients’ perceived balance between work and leisure time seems particularly important to address. Increased awareness might facilitate timely, relevant strategies to reduce stress and promote work ability.