The Dutch group "Let's Bring Them Here" wants to pick up 150 migrants and drive them to the Netherlands.
Organizers, who say they have written to Greek Prime Minister Alexis Tsipras asking him to help, concede their chances of success are slim. They won't bring back any migrants unless Greek authorities let them.
"It's Christmas, so let's believe in miracles," said Rikko Voorberg, who helped organize the convoy.
According to the Greek government, more than 14,500 migrants are stuck on islands in the eastern Aegean Sea, where official camps and other accommodations have room for under 9,000. Conditions at the camps have been heavily criticized by aid groups.
The Dutch government says it has contributed to an EU program of relocating migrants from Greece and Italy and is warning that any attempt to bring some of them to the Netherlands could be seen as people smuggling.
"Illegal transport of people without a right of residence would amount to smuggling and is punishable," Migration Minister Mark Harbers told The Associated Press. "Not only in the Netherlands, but also in the countries" the group has to drive through.
Voorberg stressed that his group isn't planning to smuggle anybody and will only bring back migrants if they are granted papers by Greece.
About 25 cars and the bus left the central Dutch city of Utrecht on Friday, hoping to arrive in Athens by Dec. 24. [AP]