The court in Nice passed sentence on Cédric Herrou on Friday morning, rejecting prosecutors' call for an eight-month suspended prison term.
It found him guilty of meeting migrants, most of them Eritrean, on Italian soil to bring them to France but not guilty of other charges, in particular housing illegal immigrants and placing them in a disused holiday home belonging to the SNCF rail company.
Herrou vowed to carry on helping migrants after the verdict.
"We'll continue our action and the threats of a prefect and the insults of one or two politicians won't stop us," he declared on the steps of the courthouse. "We'll continue because it is necessary to continue."
France's immigration law punishes people who facilitate the illegal entry, movement or residence of a foreigner in France, allowing for sentences of up to five years in prison and a fine of 30,000 euros.
In a similar case in the same region, researcher Pierre-Alain Mannoni was acquitted last month.
'Crimes of solidarity'
Rights groups say Herrou's is one of a growing number of "crimes of solidarity" with migrants and minority groups going through the French courts.
Jean-Luc Munro, a local councillor from the Green party, EELV, was in court in the northern city of Lille on Wednesday, accused of attacking a police officer because he allegedly rode into a cordon on his bicycle during an operation to clear a Roma camp.
On Thursday some 350 rights groups backed a protest in Paris at what they see as the criminalisation of humanitarian actions.
Rob Lawrie, a British lorry driver who was tried in France for trying to smuggle an Afghan girl out of Calais to join her family in the UK, was there and told RFI that such cases aim to discourage any kind of support for foreigners:
"I think they do it to discourage people from helping these people, maybe to intimidate people to stop them from helping people who they consider to be illegal," he said. "But anyone with a human heart will always continue to help these people."
Campaigners should not be branded criminals for trying to help others, he insisted.
"I’ve been walking around Paris streets buying cups of coffee for homeless people. I can help those people because they’re French but if one of those was a refugee and I bought him a coffee then I’m breaking the law, how does that work I don’t know."
France's Socialist government maintains that the crime of solidarity only applies if someone has profited from helping refugees and migrants.