Nurses contribute to a major part of the health care providers throughout the world. Their capacity for decision making is crucial in providing quality patient care. Right clinical decisions are made out of good clinical reasoning. Clinical reasoning is the process whereby clinicians collect, organize and analyse the information, make most appropriate decisions, act accordingly and reflect on during patient care situations with uncertainty. The purpose of the present study was to assess the effectiveness of Problem Based Learning strategy for Obstetric and Gynaecological   Nursing on clinical reasoning among nursing students of selected College of Nursing in Kerala. Two group post–test only design was used. Eighty eight B Sc Nursing students belonging to two consecutive batches were selected on the basis of non–random purposive sampling, 44 each in control and study group. The clinical reasoning was measured using script concordance test. The result of the study was that the mean score of clinical reasoning for control group was 29.34 ±3.612 and experimental group was 34.55± 4.051.  Problem based learning was found effective in improving clinical reasoning skills of B Sc Nursing students(t=6.3676; p<0.001)