Born on October 6, 1944 at Mahkar village in Gaya district, Manjhi's father Ramjit Ram was an agricultural labourer. Manjhi himself was put to work in the fields by landlords during his childhood days.
But as a child he had a passion for education. With encouragement provided by his father and a tutor hired for a rich landlord children, Manjhi completed studies till class 7 without attending school.
He then took admission in a high school and went on to graduate in history from Gaya College in 1967. During his student days he was active CPI member.
Manjhi took up the job of clerk with Posts and Telegraph department in 1968 but quit it in 1980 to join Congress.
That year he won on Congress ticket from Fatehpur (reserved) Assembly constituency and became a deputy minister of welfare in 1983 in the government of Chandra Shekhar Singh. He was also member of Congress government of Bindeswari Dubey.
Manjhi faced two successive defeats from Fatehpur between 1990 and 1995 Assembly elections.