Abstract: Background:Traditional teaching methods help students to acquire subject knowledge content but not knowledge construct. One important challenge in medical education is to improve the knowledge construct that enables them to translate their knowledge into useful application. Problem based learning (PBL) is emerging as one of the best methods of improving students’ knowledge construct.Objective:The study was aimed to assess the effectiveness of Problem based learning as an instructional tool in acquisition of content knowledge, critical thinking and problem solving skills in mental health issues among final MBBS students. Methodology: The study was done in a private medical college in Puducherry. Thirty students from final MBBS were randomly chosen and included in the study.They were administered with pre-test, exposed to one hour of problem based teaching and again administered with post-test the next day. Results:There was statistically significant improvement in students’ knowledge construct in mental health issues following exposure to problem based teaching methodsConclusion:PBL was found to be an effective instructional tool in fostering critical thinking and problem solving skills among medical students