The Sangh associate, who was a halwai by profession, was elected to the Delhi Assembly in 2003.
He passed away at 7:30 am at Sri Balaji Action Hospital, North Delhi, agencies said.
Garg was facing age-related health issues and was not keeping well since last few days.
Condoling his demise, Prime Minister Narendra Modi on Sunday said Garg played a pivotal role in strengthening BJP in Delhi.
“Shri Mange Ram Garg Ji had a deep connect with Delhi and that was seen in the manner in which he selflessly served the people of the city. He played a pivotal role in strengthening BJP in Delhi. His demise is saddening. My thoughts are with his family and supporters. Om Shanti,” PM tweeted along with his picture.
“Leaders like Shri Mange Ram Garg Ji are assets for any party. They work selflessly at the grassroots and touch the lives of several people through various community service initiatives. The good work Garg Ji did would continue to be remembered for years”, he added.
The mortal remains of the former BJP leader will be kept at BJP state office in Pandit Pant Marg, from 11:30am till 01:00pm for last respects, Delhi BJP chief Manoj Tiwari tweeted.
Senior BJP leader LK Advani and Home Minsiter Amit Shah paid tribute to the mortal remains of Garg at Delhi BJP office.
BJP leader Hans Raj Hans also condoled Garg's demise.