Lean is a set of operating philosophies and methods that could create maximum value for patients by reducing waste and waits when applied for health care. The study aimed to improve the service delivery of medical clinic in Base Hospital Dambadeniya (BHD) in Sri Lanka through the application of lean principles to the clinic process. Focus Group Discussions (FGDs) with patients and staff, Key Informant Interviews (KIIs) with the medical superintendent and Consultant Physician, survey of patient satisfaction with the use of self-administered questionnaire, and process mapping were carried out to gather data at pre and post-intervention stages. Long waits, congestion at the clinic, undue queuing at pharmacy, and unnecessary movements had led to poor patient satisfaction and raised concerns in the staff regarding unsatisfactory work environment. Application of lean management based on the elimination of waste, combining, rearranging and simplifying of elements of the process, reduced waits by 52%. The total requirement of staff reduced by 26% and patient satisfaction improved in selected attributes by 40%.