Mr. Majnul Ahsan joined in BCS (Judiciary) in 1981 and joined as a Munsef. Later he served in different district judgeships as munsef, Joint District Judge. He was promoted as District Judge in 2000 and posted in Khulna as Divisional Judge.
He also served as a District Judge in Chittagong. He later served as a Joint Secretary in the Ministry of Law, Justice & Parliamentary affairs and then posted as a member in Administrative Tribunal and retired from there. After his retirement, he joined as a legal adviser in Youth Commission, Basic Bank, and Bangladesh Energy Regulatory Commission and also joined as an Advocate in the High Court Division of Supreme Court of Bangladesh.