India launched its vaccination drive on 16 January, but it was limited to healthcare workers and frontline staff.
Now, people over 60 and those who are between 45 and 59 but have other illnesses can get vaccinated.
State-run hospitals will offer free jabs but people can also pay at private facilities to get vaccinated.
Mr Modi, who's 70 years old, was among the first to get his vaccine shot on Monday. He was administered a jab of Covaxin, an indigenously developed vaccine.
After receiving the jab, he took to Twitter, urging people to take the vaccine when their turn came.
"Took my first dose of the Covid-19 vaccine at Aiims [hospital]. Remarkable how our doctors and scientists have worked in quick time to strengthen the global fight against Covid-19. I appeal to all those who are eligible to take the vaccine. Together, let us make India Covid-19 free," he tweeted.
The government aims to cover 300 million "priority people" by the end of July.
Since the pandemic began, India has confirmed more than 11 million cases and over 157,000 deaths.
Much of India has reported a sharp fall in cases recently - with daily infections for the county falling to less than 20,000 from a peak of over 90,000 in September.