Mr Vaishya, who graduated in 1938, expressed his delight on Tuesday at this achievement.
"Finally, I have fulfilled my long cherished dream. Now I am a postgraduate. I decided to prove two years ago that even at this age, one can fulfil their dreams and achieve anything. I am an example," he told IANS in Patna.
Mr Vaishya reiterated that he has been trying to send a message to the youth that defeat should never be accepted.
"I want to tell them not to get upset and depressed. 'Mauka aur avsar har wakt rehta hai, kewal khud pe vishwas hona chahiye' (There will be always be opportunities for those who believe in themselves)," he said.
Admitting that it was not easy to follow the routine of a student at his age, he said: "It was really difficult for me to wake up early to prepare for the exams."
According to NOU officials, Mr Vaishya was so determined to get a postgraduate degree that he sat for a three-hour MA first year examination in 2016 and the final year exam in 2017 along with students younger than his grandchildren. He wrote in English and used nearly two dozen sheets in each exam.
Mr Vaishya has set an example for millions of people, who use age as an excuse to give up on their dreams.
Mr Vaishya was recognised earlier this year by the Limca Book of Records as the oldest man to apply for a postgraduate degree.
Mr Vaishya, who enrolled for the course in 2015, said that he has no plans to pursue a PhD.
"The idea was not to get a degree but to study economics. There are many PhD students who have superfluous knowledge," he said.
Born on April 1, 1920, in Bareilly, Uttar Pradesh, he did his graduation from Agra University in 1938 and got a degree in law in 1940.
"I failed to pursue a postgraduate programme at that time due to family responsibilities," he recalled.
A vegetarian and a lover of simple traditional Indian food, Vaishya said that he never consumed fried food and always ate in moderation.
Mr Vaishya can read without glasses and write in both Hindi and English.
"I took the help of a walker only after I fractured my back a few years ago," he said.
Mr Vaishya lives with his son Santosh Kumar in Rajendra Nagar Colony, a posh society in Patna. He has been living here for almost a decade after his wife's death.
He lived with his wife earlier in Bareilly and shifted to Patna because there was no one to look after him.