In 1915, after his father died, he moved to Bombay to support his family back home, following his elder brother. Initially he worked as a junior clerk at an office but quickly he opened a small goods store, mainly selling bidis – leaf-rolled cigarettes, and soon owned a string of eight retail shops.
In 1924 he married Sumatibai and they had three daughters and a son.
In 1933, he was introduced to his guru, Sri Siddharameshwar Maharaj, the head of the Inchegeri branch of the Navnath Sampradaya, by his friend Yashwantrao Baagkar. His guru told him, "You are not what you take yourself to be...". He then gave Nisargdatta simple instructions which he followed verbatim, as he himself recounted later:
"My Guru ordered me to attend to the sense 'I am' and to give attention to nothing else. I just obeyed. I did not follow any particular course of breathing, or meditation, or study of scriptures. Whatever happened, I would turn away my attention from it and remain with the sense 'I am'. It may look too simple, even crude. My only reason for doing it was that my Guru told me so. Yet it worked!"
Following his guru's instructions to concentrate on the feeling "I Am", he utilized all his spare time looking at himself in silence, and remained in that state for the coming years, practising meditation and singing devotional bhajans.
After an association that lasted hardly two and a half years, Sri Siddharameshwar Maharaj died on November 9, 1936 , though by that time he had done his task. Maruti had reached self-awareness. Soon he adopted a new name, 'Nisargadatta' meaning the one who dwells in the natural state. He was also appointed as the spiritual head of the Inchegeri branch of Navnath Sampradaya, the 'Nine Masters’ tradition, a place he retained through his life.
In 1937, he left Mumbai and travelled across India. Through realising the shortcomings of a totally unworldly life and the greater spiritual fruitfulness of dispassionate action, he eventually returned to his family in Mumbai in 1938. It was there that he spent the rest of his life.
Between 1942-1948 he suffered two personal losses, first the death of his wife, Sumatibai, followed by the death of his daughter. He started taking disciples in 1951, only after a personal revelation from his guru, Sri Siddharameshwar Maharaj.
After he retired from his shop in 1966, Sri Nisargadatta Maharaj continued to receive and teach visitors in his home, giving discourses twice a day, until his death on September 8, 1981 at the age of 84, of throat cancer.
Many of his talks were recorded, and these recordings form the basis of I Am That and all his other books. His words are free from cultural and religious trappings, and the knowledge he expounds is stripped bare of all that is unnecessary.
Summed up in the words of Advaita scholar and a disciple, Dr. Robert Powell, "Like the Zen masters of old, Nisargadatta's style is abrupt, provocative, and immensely profound -- cutting to the core and wasting little effort on inessentials. His terse but potent sayings are known for their ability to trigger shifts in consciousness, just by hearing, or even reading them.”