Del Potro reached his second straight final at the Rotterdam tournament by beating Grigor Dimitrov 6-4, 6-4. Benneteau then defeated fellow Frenchman Gilles Simon 6-4, 7-6 (2), with Simon troubled by an upper thigh injury throughout much of the second set.
Del Potro, the 2009 U.S. Open champion, lost to Roger Federer in last year's final but he won't have to face him this year after Benneteau eliminated the Swiss star in the quarterfinals.
"It was not as good as yesterday, but who cares? I won," Benneteau said.
In the first semifinal, the 6-foot-6 del Potro's powerful serves and groundstrokes were too much for the swift and agile Dimitrov, who was attempting to reach his second ATP final of the year after losing to Andy Murray in Brisbane, Australia, last month.
Del Potro broke in the third game of each set and rarely let Dimitrov attack his serves. Del Potro hasn't dropped a service game in the tournament.
"I am serving well, but I need to serve a little better tomorrow in the final," he said. "I saved a couple of break points, so I need to improve myself."
Dimitrov, a crowd favorite at Rotterdam's Ahoy Arena, delighted the fans with a between-the-legs shot from the baseline following a powerful drive from del Potro. But the 21-year-old Bulgarian faded in the second set, possibly weary from Friday's grueling three-set quarterfinal victory over Marcos Baghdatis that lasted 2½ hours.
The all-French semifinal went with serve until the ninth game of the first set when Benneteau capitalized on his third game point by chasing down Simon's backhand and playing a cross-court forehand that Simon scrambled to reach and netted.
Simon forced a break point in the next game, but Benneteau saved it and went on to serve out the set. In the next game, Simon grabbed at the back of his left leg at the top of his thigh.
Despite the injury, he broke Benneteau in the second game, only to take an injury timeout for off-court treatment when Benneteau broke back in the fifth game.
When Simon returned, he managed to take the set to a tiebreak, but Benneteau easily won it to take him a step closer to his first ATP title.
"It's never easy to play against a friend, a Frenchman," Benneteau said after beating his sometime practice partner and Davis Cup teammate.
Benneteau has reached seven singles finals, but never won one.
"I'm looking forward to my first title and I will be the happiest man if it's here tomorrow," he said.