In the first round of the main draw, he will meet world number 35 Matteo Arnaldi of Italy in the clay court tournament.
The 26-year-old Nagal was following the footsteps of the legendary Ramesh Krishnan, who had made it to the main draw of the same tournament in 1982.
Nagal had beaten world number 63 Flavio Cobolli of Italy 6-2 6-3 in the first round of qualifying event.
“Absolutely thrilled to have made it to the main draw in Monte Carlo! Really appreciate the support and well wishes from India and around the globe. Can’t wait for my next match!,” Nagal tweeted after the win.
Nagal has been in the spotlight since making it to the main draw of the Australian Open in January, where he had beaten Alexander Bublik of Kazakhstan before bowing out in the second round. He then emerged triumphant in the Chennai Open before playing two more Challenger competitions, along with an ATP 500 competition (Dubai Championship) and two ATP 1000 Masters (Indian Wells and Miami).