He joined Indian Civil Services in November 1921 and was posted as Sub-Collector at Madras. He later on served as Joint Magistrate and District and Session Judge till February 1943 when he was appointed Additional Judge of the Madras High Court. In September 1945 he was confirmed as a Judge of Madras High Court.
Justice Shahabuddin was appointed as a Judge of Dacca High Court after Partition. He served on Indo-Pak Boundary Disputes Tribunal in 1949-50. He became the Chief Justice of Dacca High Court in February 1950. In 1953 he was appointed as a Judge of the Federal Court. From 22 December 1954 to 14 June 1955 he acted as the Governor of East Bengal (Pakistan). He became the Chief Justice of Pakistan in 1955. Justice Shahabuddin also chaired the Constitution Commission.