In a tight tussle, Spaniard Feliciano Lopez edged out the Australian youngster in a 6-4 6-7 (4-7) 7-6 (7-1) result.
As the two battled it out for almost two-and-a-half hours, Lopez hit 21 aces but still struggled to land his first serve – less than half of his attempts were in – although Tomic was unable to take advantage.
The Australian broke on just two occasions during the match but shaded a tight second set before serving nine aces of his own in the decider, only to be undone by the world number 29 in the tie-break.
Lopez will now play Stanislas Wawrinka of Switzerland in the second round.
Croatian Marin Cilic, meanwhile, won his first game back from a drugs ban with a three-set success against Igor Sijsling in the first round of the BNP Paribas Masters.
Cilic had a nine-month ban – given to him for testing positive to banned stimulant nikethamide – slashed to four months by the Court of Arbitration for Sport last week.
And he returned to tennis as a winner, coming from behind to defeat Dutchman Sijsling 5-7 6-1 6-4 in one hour and 41 minutes at the ATP 1000 event in Paris.
The Croatian put in a typically powerful performance, smashing 21 aces while he won 35 of his 39 points on first serve on the hard court.
Cilic – who has dropped to 41st in the world rankings as a result of his inactivity - also made three breaks as he produced a terrific victory.
He said afterwards: "I felt like a kid playing for the first time. The feeling was amazing, just to be back on the court, to be competing. I enjoyed every moment."
Cilic faces a tough ask in the next round though, with Argentine Juan Martin del Potro waiting for him, fresh from defeating Swiss star Roger Federer in Sunday's Swiss Indoors Basel final.
Spaniard Fernando Verdasco also booked his spot in the second round with a win over Ernests Gulbis.
Verdasco converted just one of his 11 break points, making his 7-6 (7-3) 7-6 (7-5) triumph over Latvian Gulbis harder than it needed to be, while Japan's Kei Nishikori thrashed Frenchman Julien Benneteau 6-4 6-2.
Nishikori will meet French star Jo-Wilfried Tsonga in the next stage of the tournament.
In an all-French clash, world number 26 Benoit Paire was stunned by Pierre-Hugues Herbert, going down 6-2 6-2 despite a gap of 123 places between the two in the ATP rankings.
Other results saw German Philipp Kohlschreiber defeat Italian Andreas Seppi 6-3 3-6 6-4, Czech Lukas Rosol eased past France's Jeremy Chardy 6-3 6-4 and Dutch qualifier Robin Haase beat Uzbek Denis Istomin 7-6 (10-8) 6-3.
Colombian qualifier Santiago Giraldo also enjoyed success, toppling Frenchman Adrian Mannarino 6-3 2-6 6-4.