The activists' departure, after charges against them were dropped, removes an irritant in Putin's prickly ties with the West as Russia prepares to host the 2014 Winter Olympics in Sochi in February.
The demonstrators had faced up to seven years in jail for a protest at an offshore rig.
The first activist to leave took a train to Finland late on Thursday and by late Friday (local time), 25 of the 26 foreigners among the group Greenpeace dubbed the "Arctic 30" had left Russia, the Netherlands-based organisation said.
"It's over. We're finally, truly free," said Alex Harris, 27, from Devon in Britain.
"It feels like the moment I've been waiting for, and my family too, but also for millions of people around the world who have worked for this," she said in a statement.
Russia's treatment of the activists from 18 countries - who spent two months in detention and at one point faced up to 15 years' jail on piracy charges - had drawn criticism from Western nations and celebrities such as ex-Beatle Paul McCartney.
"The support worldwide has been humbling. Thank you," Dutch activist Faiza Oulahsen said on Twitter on Friday. She tweeted: "On my way back to Amsterdam after nearly 4 incredible months."
Criminal charges were dropped under an amnesty proposed by Putin and approved by parliament this month in a move Kremlin opponents said was timed to improve Russia's image before the Olympics.
Russia says activists endangered lives and property at state-controlled Gazprom's Prirazlomnaya offshore platform, which some of the activists tried to scale in the protest in September in the Pechora Sea.
Greenpeace said the boarding of its icebreaker, Arctic Sunrise, was illegal and that the protest was peaceful.
Putin said earlier this month he believed the activists may have been may have been carrying out an order to undermine Russia's development of Arctic energy resources, which he has set out as a priority.
