The second-seeded Frenchman had won 11 of his last 13 matches coming in, including titles at Metz and Vienna. But Tsonga trailed early due to unforced errors and the smooth backhand of the 19-year-old wild card, who was playing his first match against a top-10 player.
Top-seeded David Ferrer opened his title defense by easily beating fellow Spaniard Fernando Verdasco 6-3, 6-2, while third-seeded Frenchman Gael Monfils also advanced with a 6-3, 6-1 victory over Albert Montanes of Spain.
Ferrer reeled off 10 straight games after the Davis Cup teammates were even at 3-3 in the first set, with Verdasco overcome by frustration after making nearly 50 unforced errors.
Ferrer clinched the win on his third match point to set up a second-round match against Canadian qualifier Vasek Pospisil.
"It wasn't easy at the start, but he made more mistakes than normally and the game ended well," Ferrer said. "Playing at home motivates me so much more. It makes it a lot easier for me."
Tsonga complained about the streaks of sunlight across the indoor court at City of Arts and Sciences, but settled toward the close of the second set after Marti double-faulted and was broken in the 11th game.
Tsonga, who smacked 10 aces, was more disciplined in the final set and used his experience when Marti faltered. Trailing 4-1, Marti never recovered against a player still vying to clinch his place at the season-ending ATP World Tour Finals.
"He played better than me in the first set, but after that I recovered," said the seventh-ranked Tsonga, who is now five points behind Tomas Berdych in qualifying for the Nov. 20-27 tournament, in which three spots remain up for grabs.
Marcel Granollers of Spain provided the first upset of the indoor tournament with a 6-3, 6-4 win over seventh-seeded Alexandr Dolgopolov of Ukraine. Juan Carlos Ferrero and Kevin Anderson also advanced with victories.