The striker crept into an enlarged, 30-man provisional squad for the Euros named by coach Raymond Domenech nine days ago by virtue of his superb goalscoring form for St Etienne in the final weeks of the Ligue 1 season.
He was only given 45 minutes against Ecuador but he lapped up his first taste of international football by firing in from long range on the hour mark and volleying home splendidly in the 86th minute to seal victory for Les Bleus.
Domenech trims his squad down to 23 on Wednesday and he will be hard-pushed to ignore Gomis now, given the 22-year-old's two-goal salvo.
Gomis aside, few fringe players for Les Bleus put their hand up for selection for the Euros in what was a tough game against a well-organised Ecuador team, who had the better chances in the first half.
With Domenech putting out an experimental line-up, it was to be expected that their play was not so fluent early on.
The likes of Alou Diarra, Samir Nasri, Hatem Ben Arfa and Djibril Cisse - none of whom are secure of a place in the final 23 - all started.
And it was Nasri who had the match's first decent chance, the wantaway Marseille playmaker firing an effort straight at Marcelo Elizaga from distance in the 27th minute.
Cisse then headed a Nicolas Anelka centre just over before Ecuador finally came to life.
Lilian Thuram, the France captain, needed to be at his most alert to clear two efforts by Carlos Tenorio off the line in as many seconds after the Ecuador striker had rounded goalkeeper Sebastien Frey.
A wrong-footed Frey then produced a smart save with his feet to keep out Segundo Castillo's 12-yard drive just before the half-time whistle.
By this point, the crowd of around 20,000 may have been fearing the worst but the half-time introduction of Gomis changed everything.
In the 53rd minute, he ran on to a through-ball by another substitute, Mathieu Flamini, but fired his snap-shot just wide from the angle.
The striker got it right six minutes later when he put France ahead.
The increasingly influential Ben Arfa fed him, and despite a heavy first touch, Gomis turned his marker and smashed a 25-yard drive into the top corner for his first international goal.
Les Bleus piled forward in search of a second in the final 15 minutes.
Firstly, Ben Arfa created space for himself 30 yards out before seeing his powerful, long-range effort turned to safety by Elizaga.
Anelka was then released down the right, but his side-footed finish could only find the side-netting from a narrow angle.
Gomis had the final word, though, when he attacked Anelka's cross and produced a flying right-foot volley from 10 yards that gave Elizaga no chance.