Nadal and Djokovic are vying for the year-end No. 1 ranking. Nadal will guarantee it for the fifth time if he wins the Paris Masters for the first time, while Djokovic is chasing a fifth title at Bercy Arena and a sixth year-end finish as No. 1.
Djokovic, who lost to the Greek player in the Shanghai quarterfinals three weeks ago, did not concede a break point to Tsitsipas.
It could have been an even quicker victory, considering Tsitsipas saved three set points at 0-5, 0-40 in the first set and held serve.
"I played one of the best matches of the season. I prepared myself very well for this match," Djokovic said. "[After losing in Shanghai], I went through the videos, understanding what I did well, what I didn't do so well.
"I served well. I read his serve very well, as well. Put him under pressure constantly."
Djokovic, a four-time champion in this event, broke Tsitsipas in the third game of the second set, then held and broke to love for 4-1. Tsitsipas, who dropped his serve four times, appeared to hurt his left ankle when retrieving a shot near the baseline in the second set.
Nadal had a more demanding contest against Tsonga, with the first set tiebreak reaching 3-3 after Nadal double faulted. Nadal, however, broke the unseeded Frenchman at the start of the second set and cruised from there.
"It was a tough first set where I had to play at a very high level," Nadal said after beating Tsonga for the 10th time in 14 meetings.
Nadal is guaranteed to finish the year as No. 1 if he wins the Paris Masters for the first time.
Nadal is 1-1 in career meetings with Shapovalov.