Two Frenchmen who had previous court convictions were given four-month jail terms.
The others, who included an Italian woman, a Swiss man and a Swiss-Belgian man, received suspended six-month sentences.
The activists, whose supporters dubbed them the “Briancon 7”, took part in a solidarity march of 100 people escorting some 20 migrants over an Alpine pass in April this year.
They were responding to a blockade at a nearby pass set up by several dozen far-right activists from Generation Identitaire (Identity Generation) who want to keep migrants out.
The activists had argued they took part in a “spontaneous demonstration” intended only to counter the far-right protest.
France's Constitutional Court ruled in July that people could not be prosecuted for aiding migrants in distress, saying this went against the basic French principle of solidarity.
However the court's ruling does not allow people to directly facilitate illegal border crossings.
“Everyone here can demonstrate in order to defend their ideas, even the most radical, but without breaking the law,” prosecutor Raphael Balland said at their trial.
The activists have 10 days to appeal the ruling by the court in Gap, where around 100 supporters gathered outside the courthouse Thursday.
The Gap sentencing came a day after another migrant activist, Cedric Herrou, saw his suspended prison term overturned by France's top appeals court on Wednesday.
Herrou, an organic olive grower in southern France, had been charged with illegally offering aid to migrants at his farm near the Italian border.
The appeals court cited the Constitutional Court's decision against prosecuting so-called “crimes of solidarity”.