Sankrityayan was a multilingual linguist, well versed in several languages and dialects, including Hindi, Sanskrit, Pali, Bhojpuri, Urdu, Persian, Arabic, Tamil, Kannada, Tibetan, Sinhalese, French and Russian. He was also an Indologist, a Marxist theoretician, and a creative writer. He started writing during his twenties and his works, totalling well over 100, covered a variety of subjects, including sociology, history, philosophy, Buddhism, Tibetology, lexicography, grammar, textual editing, folklore, science, drama, and politics. Many of these were unpublished.He translated Majjhima Nikaya from Prakrit into Hindi.

One of his most famous books in Hindi is Volga Se Ganga (A journey from the Volga to the Ganges) — a work of historical fiction concerning the migration of Aryans from the steppes of the Eurasia to regions around the Volga river; then their movements across the Hindukush and the Himalayas and the sub-Himalayan regions; and their spread to the Indo-Gangetic plains of the subcontinent of India. The book begins in 6000 BC and ends in 1942, the year when Mahatma Gandhi, the Indian nationalist leader called for the quit India movement.

This book was translated by K.N. Muthiya-Tamilputhakalayam in Tamil as Valgavil irundu gangai varai and is still considered a bestseller. The Kannada translation done by B.N Sharma as Volga Ganga . The Telugu translation inspired many readers. Volga muthal Ganga vare, the Malayalam translation, became immensely popular among the young intellectuals of Kerala and it continues to be one of the most influential books of its times. The Bengali version is Volga Theke Ganaga [ভোল্গা থেকে গঙ্গা], which is still acclaimed by the critics.

More than ten of his books have been translated and published in Bengali. Mahapandit was awarded the Padmabhushan in 1963 and he received the Sahitya Akademi Award in 1958 for his book Madhya Asia ka Itihaas.

He maintained daily diaries in Sanskrit which were used fully while writing his autobiography. In spite of profound scholarship, he wrote in very simple Hindi that a common person could follow. He wrote books of varied interest. He was aware of limitations of Hindi literature and singularly made up the loss in no small measure.

The historian Kashiprasad Jaisawal compared Rahul Sankrityayan with Buddha. Rahuls personality was as impressive and memorable as are his achievements. He traveled widely and wrote in five languages — Hindi, Sanskrit, Bhojpuri, Pāli and Tibetan. His published works span a range of genres, which include autobiography, biography, travelogue, sociology, history, philosophy, Buddhism, Tibetology, lexicography, grammar, text editing, folklore, science, fiction, drama, essays, politics, and pamphleteering.

His travels took him to different parts of India, including Ladakh, Kinnaur, and Kashmir. He also travelled to several other countries including Nepal, Tibet, Sri Lanka, Iran, China, and the former Soviet Union. He spent several years in the Parsa Gadh village in the Saran District in Bihar. The villages entry gate is named Rahul Gate. While traveling, he mostly used surface transport, and he went to certain countries clandestinely; he entered Tibet as a Buddhist monk. He made several trips to Tibet and brought valuable paintings and Pali and Sanskrit manuscripts back to India. Most of these formed a part of the libraries of Vikramshila and Nalanda Universities. These objects had been taken to Tibet by fleeing Buddhist monks during the twelfth and subsequent centuries when the invading Muslim armies had destroyed universities in India. Some accounts state that Rahul Sankrityayan employed twenty-two mules to bring these materials from Tibet to India.He has a grandson named Prakhar Sankrityayan currently living in India. Patna Museum, Patna, has a special section of these materials in his honour, where a number of these and other items have been displayed.