The present study examines the relationship between teacher development programmes and the professional competency of in-service teachers in Ratnagiri District. The study focuses on various dimensions of teacher development programmes such as training content, duration, methodology, and follow-up support, and analyzes their impact on professional competencies including subject knowledge, pedagogical skills, classroom management, assessment practices, and professional attitudes. A descriptive survey method was employed, and data were collected from in-service teachers working in secondary schools of Ratnagiri District using standardized questionnaires. Appropriate statistical techniques were used to analyze the data and determine the nature and extent of the relationship between the variables. The findings of the study reveal a significant positive relationship between participation in teacher development programmes and the level of professional competency among in-service teachers. The study highlights the importance of well-structured and continuous professional development programmes in enhancing teachers’ effectiveness and recommends strengthening such initiatives to improve overall educational outcomes.