Alongwith his higher studies Nagarjun worked for his livelihood. For many years he studied and was semi-employed in Calcutta and later moved to Saharanpur (U.P.) to work as a full time teacher. His insatiable urge for knowledge especially in the Sanskrit treatises and philosophical discourses, and Buddhist scriptures took him to Sri Lanka where he accepted Buddhism in the monastery of Kelania
Nagarjun actively participated in politics. Nagarjun was influenced by the writings of Marx, Lenin and Stalin. He supported the armed revolt of the peasants of Naxalbari in West Bengal and was later passionately involved in the anti-government agitation in Bihar under the leadership of Jai Prakash Narayan in 1974. During this period he was jailed for eleven months.
Nagarjun's novels like Balchanma, Ratinath Ki Chachi, Baba Batesarnath and Varun Ke Bete are landmarks in Hindi fiction depicting the rural reality in an unparalleled manner. He wrote poems both in Maithili and Hindi. He published two Maithili poems, Boorh Var and Vilap in 1941 in the form of pamphlets and sold them on passenger trains. He wrote two poems in Hindi Shapath and Chana Jor Garam, which were circulated in 1948 and 1952 respectively. His first collection of twenty-eight poems in Maithili, entitled Chitra appeared in 1949. It is considered the first modern classic, which is used as a standard university textbook in the Maithili language.
By 1953, there was a change in the themes of his poems, Nagarjun now shifted from lyrical romanticism, and wrote on the rebellion of Telangana, Mother India and famine. In 1950, he wrote a piece of satire in just ten lines about "the five worthy sons of Mother India". He even wrote a short poem in eight lines on "The Famine and After", the poem deals with famine, hunger, anguish, and apathy. In 1948, his novel Ratinath Ki Chachi (Ratinath's Aunt) was published. This novel consisting of 113 pages is autobiographical and one of the most realistic and feminist Hindi novels. The novel is a harrowing tale of abject poverty and extreme exploitation. His next novel Varun ke Bete was published in 1956, is an unconventional work dealing with the story of the low-caste fishermen, who fights for the fishing rights and tries to form a fishermen's cooperative. He wrote thirteen novels, eleven in Hindi and two in Maithili. Most of his novels center around a social, economic or political theme, set in rural or semi-urban Bihar. His novels mostly narrate the story of the destitute and the exploited, chiefly amongst them are women and children.
Nagarjun unconsciously became the forerunner of the Annchalik Upanyas (the Regional Novel) in Hindi. Apne Khet mein is his last published collection of Hindi poems in 1997, which consists of personal poems like Na Sahi and Aur Phir Dhikai Nahin Di and parodies the artist M.F.Hussain and the political leader Laloo Yadav. Hua Gittiyon Men Ras ka Sanchar is another moving poem on the pathetic life of the rickshaw pullers of Calcutta.
He was awarded the Bharat Bharati Award by the Uttar Pradesh government for his literary contributions in 1983. For his collection of poems Patraheer Nagna Gaachhin in Maithili, he was given the Sahitya Akademi Award in 1968.
He passed away in November 1998.