Abdul Sattar Siddiqui was a well-known researcher of Urdu. Historical and comparative linguistics were his major areas of research. He had complete command on Urdu, Arabic, Hindi, Pahlavi and English and also had knowledge of Syriac, Hebrew and the Turkish languages. Maqalāt-i Siddīqī and Muʿarrabāt-i Rāshidī are his important works that also reflect his skill and understanding of his discipline. All his major contemporaries including Hafiz Mahmood Shirani, Syed Salman Nadvi and Abdul Majid Daryabadi held a very high opinion of him. This article deals with Abdul Sattar Siddiqui’s valuable contribution to the world of knowledge and research.