The victory keeps Nadal at No 1 in the world ranking as he retained his title and followed up his victory in Monte Carlo last week.
World number one Nadal also extended his winning streak on clay to 44 consecutive sets as he downed Goffin for a third time in three meetings on the red dirt surface he has dominated for more than a decade.
Tsitsipas was feeling the heat with the sun beating down after that earlier rainfall, the outsider ballooning a forehand high and wide to gift Nadal a break in the opening game of the second set.
On current form, Nadal is the undoubted favourite for the title in Paris, and it would come as no suprise if his name is once again engraved on the trophy come June 10. Nadal has won 5 titles there and will be looking to achieve his 6th one as well. Only Jimmy Connors, Roger Federer and Ivan Lendl are ahead. Notably, the 16-time Grand Slam champion had pulled out of Australian Open in the quarter-final round with a hip injury, which recurred and stopped him from featuring in the Sunshine tournaments, Indian Wells and Miami Open.
The 63rd-ranked Tsitsipas was trying to become the first Greek to win an ATP Tour title.
After the win, Nadal dived into a pool at the venue along with some of the tournament's ball boys and ball girls.
Upcoming Apple iPhone Could Be Missing Some Features
A new, lower-cost iPhone will use an LCD display that's about half the cost of the OLED screen in the iPhone X . To keep the price in check, these iPhones are likely to lose the 3D Touch technology as well.
The 31-year-old is now sitting top of the ATP world rankings and playing some of the best tennis of his career.
"I knew the chances to win were small, but my confidence was rising in every match and while I was expecting a little better today, congratulations to Rafa", Tsitsipas said.
"I'm very happy for the victory against a very hard opponent", said Nadal. Tsitsipas is the youngest Barcelona finalist since Nadal in 2005. It was a great final for me and the 11th title here means a lot.
Tsitsipas, 19, is the second-youngest player in the ATP top 100.
"I have watched millions of his matches on clay", Tsitsipas said.