Mishra, 84 declared brought dead at the Fortis hospital in Vasant Kunj in south Delhi, at around 9.50 p.m. on Friday, hospital sources said.
He was suffering from cardiac problem for some time.
A career diplomat, Mishra was Principal Secretary to Prime Minister Atal Bihari Vajpayee before he was appointed NSA.
He had earlier retired as Secretary in the External Affairs Ministry after having served as India’s Permanent representative to the U.N.
He had played a crucial role in assisting Vajpayee during the Kargil conflict in 1999.
Born on 29th September 1928, Mishra was ambassador and India’s permanent representative in Geneva and India’s ambassador to Indonesia.
He was also India’s permanent representative to the UN from June 1979 to April 1981. He continued with the UN, on deputation, till June 1987.
He was the son of Dwarka Prasad Mishra, a former chief minister of Madhya Pradesh, considered a staunch politician from the Congress and very close to Indira Gandhi
After the fall of the NDA government in 2004 and the fading away of Vajpayee from the political scene, Mishra distanced himself from BJP and often criticised its stand on various foreign policy issues.