The aim of this study was to determine the frequency and determinants of sharps injuries among private health practitioners in slum areas of Karachi, Pakistan. All practitioners with at least 1 year of experience in a private medical clinic were asked to complete a self-administered, structured questionnaire (317/397 responded). Only 7.9% of practitioners were qualified from medical school, 12.3% were registered nurses and 8.8% lacked any professional qualifications. At least 1 sharps injury in the previous 12 months was reported by 26.7%, mostly due to needle recapping. Only 25.2% reported using a new syringe for each patient. In multivariate regression analysis shorter work experience, < 14 years of schooling, > 20 patients per day, administering ≥ 30 injections per day, reuse of syringes and needle recapping after use were significantly associated with sharps injury in the past year. Better awareness and training on standard precautions is needed for private practitioners in slum areas of Karachi.