Robert Lawrie, 49, told a French court he had acted after the child's father asked him to save his daughter, Bahar Ahmadi, from the squalor of the notorious camp in the northern port of Calais known as "The Jungle", and take her to relatives in England.
"It was irrational, I wasn't thinking clearly. I tried to make sure she could join her family," an emotional Lawrie said, speaking through a French interpreter.
In its verdict, the court in Boulogne-sur-Mer said Lawrie would have to pay 1,000 euros (USD 1,085) "for endangering life" if he re-offended.
Lawrie had faced the prospect of a maximum of five years in prison and a 30,000-euro (USD 33,000) fine for illegally aiding someone to enter a country.
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Bahar and her father are now back living in the camp and were present in court to support Lawrie.
Lawrie, a father-of-four from northern England, had visited The Jungle several times to build shelters for the thousands of residents living there who are desperate to reach Britain on ferries or through the Channel Tunnel.
But French police stopped Lawrie with the girl after he passed British customs at the French port when sniffer dogs detected two Eritrean migrants who had sneaked into the back of his van.
Lawrie says he did not know the two Eritreans were hidden in his vehicle.
Speaking to AFP in November, Lawrie said: "Who in their right mind would rather a child live in a tent on a chemical dump than allow me to take that one child to her family five miles (eight kilometres) from where I live?"
Lawrie told the court he did not have contact with any of the girl's relatives in Britain and had only been given an address.
"It was a very stupid decision," he told the court.
Migrants have been gathering around Calais for years, but the Jungle grew rapidly in early 2015 as the migration crisis took hold.