Begum, 76, was admitted to a hospital in suburban Andheri on May 3, a family member told PTI today.
Doctors have said there is a small hole in her heart, the member said.
Begum, who sang the evergreen song "Kabhi tanhaiyon mein hamari yaad ayegi," from the 1961 movie "Hamari Yaad Aayegi", has not been keeping well for the last few years.
Through the 1950s and 1960s, she worked with the best music directors in the film industry, collaborating with S D Burman, Shankar Jaikishan and Khayyam for movies that starred screen legends like Sunil Dutt, Nargis and Rajendra Kumar.
Her son who used to freelance as a driver and his wife live in the same house.
Mubarak Begum was born in Rajasthan. She moved to Mumbai when she was 10-year-old. Among her favourite memories is singing "Woh na aayenge palat kar" from "Devdas" which released in 1955 starring Dilip Kumar and Vaijayantimala.