Mantri was born into a Pune-based textile business family, which used property investments as a secondary source of income. In 1987, Mantri completed his first real estate construction project. Since it proved successful, the textile business was sold off to focus completely on real estate.

In 1999, Mantri founded Mantri Developers Pvt Ltd, where he is currently the chairman and managing director. He has served as the Vice-President at CREDAI since April 2013.[2]Mantri is a Co-Founder at Forum Synergies (India) PE Fund Managers Pvt Ltd.[3][4] and a Member of the Board of Trustees at Indus International School Bangalore Earlier in his career, Sushil Mantri served as a partner to Morgan Stanley real estateMantri completed his tenth standard from Pune in 1978. He is a Commerce graduate from Pune University and an alumni from Harvard Business School.