The former attorney general died in a Dhaka hospital late on Monday night. He was 80.
A London-based Bangladeshi lawyer, who practises in the Supreme Court in Dhaka, described him as "perhaps the most cerebral lawyer in our recent history".
He has left behind his wife, two sons, a grandson and a granddaughter.
He was the first lawyer in Bangladesh to write a book researching the Constitution.
The Supreme Court had sought his statement as amicus curiae in several significant cases.
A relative of his, lawyer Sheikh Md Morshed, said the former attorney general was suffering from geriatric diseases including complications in the lungs.
A lawyer of Islam’s chamber said he had been at the United Hospital’s ICU for around two months and taken to Singapore once in this period for better treatment.
Born in Rangpur in 1936, Mahmudul Islam passed his higher secondary level from Rangpur Carmichael College.
He received his law degree from Dhaka University after completing honours and masters in political science.
His father Azizul Islam was a renowned lawyer in Rangpur.
Starting his career at Rangpur Bar, he later got enlisted at the High Court.
He worked as a junior with lawyer Birendra Nath Chowdhury and then with Syed Ishtiak Ahmed.
After the independence of Bangladesh, he received his LLM degree from Indiana University in the US.
He became assistant attorney general in 1972.
He served as the state’s top legal officer from 1998 to 2001. He resigned on the very day the government took charge after the eighth parliamentary election.
His book on the Constitution – ‘Constitutional Law of Bangladesh’ – is the first on the issue in Bangladesh.
Other books he wrote include ‘Law of Civil Procedure’ and ‘Interpretation of Statutes and Document’.
His two sons – Asif Islam and Arif Islam – are both engineers and currently in Canada.
His relatives said they are planning to bury him in Rangpur after his sons arrive on Wednesday.