He was born into one of the most distinguished Sri Lankan Moor families of that time as the youngest of twelve siblings.

Originally a small movement, in three months it grew into the most powerful Muslim organization in Ceylon.

[citation needed] His most prominent achievements include ranking second in the Inter-Arts Examination in the First Division, and obtaining a B.A.

Some of his other accomplishments were the gold medal of the All-India Public Speaking Competition, the Aligarh – The Oxford Meston Prize in 1937 for outstanding debating ability, and being appointed editor of the university's magazine for two successive years.

[3]While he was enrolled at Aligarh, Mahmud persuaded Muslim leaders in the Second Round Table Conference at London to support the Indian independence movement; the people that he persuaded included Shaukat Ali, Muhammad Ali Jinnah, Muhammad Iqbal, Mukhtar Ahmed Ansari, Muhammad Shafi, Zafar Ali Khan, Syed Mahmud, Bacha Khan, Mirza Ismail, and Syed Sultan Ahmed.

[citation needed] On Mahmud's arrival in Sri Lanka from Aligarh, the Muslim League organized a highly attended reception to him.

[3] In 1938, Badi-ud-din Mahmud gave a speech at the birthday celebrations of Muhammad at Galle Face Green.

Mahmud furthered his reasoning:[3] If this is done, all misunderstanding will disappear and there will be perfect harmony between the Sinhalese and the Moors.

[3] In the same year, Badi-ud-din Mahmud organized one of the largest demonstrations of the time among Muslims, a mass rally at Galle Face Green in support of the Arabs in Palestine.

Mahmud developed a uniform of pajamas, frocks, and a dupatta (scarf) for girls at Zahira College; it is now widely accepted in Muslim schools in Sri Lanka but was at first rejected by most.