The crew includes Alexandre Paul of Montreal and Paul Ruzycki of Port Colborne, Ont., and the charge they both face can result in a 15-year prison term upon conviction.
Greenpeace denies any wrongdoing and describes the charges as absurd. The mother of one of the Canadians says they make no sense.
''I think we can agree that piracy involves weapons and taking control of another vessel. Greenpeace did nothing like that,'' Paul's mother, Nicole Paul, said in a phone interview from Pike River, Que., south of Montreal.
Nicole Paul said her son has travelled the globe the last seven years to defend his ideals and that he once spent a night in prison in Scotland before being released without charge.
''Nothing has ever happened like this. They're being treated like terrorists. It's not easy.''
She said the activists were protesting peacefully.
In Russia, the Investigative Committee said in a statement that the piracy charge was filed Thursday against 16 members of the crew, including a prominent Russian freelance photographer.
The crew's other 14 members were similarly charged Wednesday.
The Russian Coast Guard seized the Greenpeace ship and all the people it was carrying following the Sept. 18 protest at the offshore platform owned by Russian state-controlled energy giant Gazprom.
The activists are now in custody in the northern city of Murmansk.
In a news release from the group, Greenpeace International executive director Kumi Naidoo said the charges are being laid against those "whose only crime is to be possessed of a conscience."
Naidoo called the charges an assault on the principle of peaceful protest and added: "It is utterly irrational, it is designed to intimidate and silence us, but we will not be cowed.”
Christy Ferguson, Arctic Campaign Co-ordinator with Greenpeace Canada, said the activists did not do anything that resembled piracy.
“These brave individuals stood up against the destructiveness of Arctic oil drilling on behalf of all of us," said Ferguson in the statement.
Activists from Canada, Argentina, Brazil, Britain, Finland, the Netherlands, Poland, Russia and Sweden were among 30 people who were on board the Greenpeace ship.
A Canadian Foreign Affairs Department spokesman said the government is aware of the situation involving two Canadians in Murmansk and that consular services were being provided "as required." The spokesman said due to the Privacy Act, no more information could be shared on the matter.
--With files from Melanie Marquis in Montreal
--With files from The Associated Press