He finished elementary as the class valedictorian at Cotabato Central School in Cotabato City on 1949. He was the first honorable mention when he finished his high school studies at Cotabato High School. Right after finishing high school, he took up Bachelor of Laws at the.
He was admitted to the Bar on 1959.
Datumanong entered politics when he was elected as Vice-Governor (1963–1967) then as Governor (1967–1971) of Cotabato. When the province of Cotabato was split to the provinces of Maguindanao, Sultan Kudarat, and North Cotabato, he was elected as the first governor of Maguindanao in 1973 and served until 1975. He was then elected to the Regular Batasang Pambansa from Maguindanao in 1984.
In 1992, Datumanong was elected to the Philippine House of Representatives to represent Maguindanao"s Second District.
He served until 2001 when he was appointed by President Gloria Macapagal-Arroyo as Secretary of Public Works and Highways. In 2003, he was Secretary of Justice and served until his resignation in the same year.
He was reelected to the Philippine House of Representatives in 2007.
