The lower house of parliament, the State Duma, also voted to increase maximum sentences for a range of terrorism and sabotage offences and introduced a new law that punishes those who help execute the legal decisions of international organisations that do not include Russia with up to five years in prison.
That move was a direct response to the International Criminal Court issuing an arrest warrant for President Vladimir Putin last month in connection with the deportation of Ukrainian children to Russia.
The amendments - which need to be approved by Russia's upper house, the Federation Council, before being signed into law by Putin - come as rights groups say Russian authorities are ramping up a campaign to quash the few voices of opposition that remain in the country. The previous maximum sentence for treason was 20 years.
On Monday, a Moscow court sentenced opposition politician activist Vladimir Kara-Murza to 25 years in prison on treason and other charges, the harshest sentence handed down to a Kremlin critic since Russia invaded Ukraine last February.
Human Rights Watch has said the Kremlin uses such cases "to instil fear in the Russian people and eradicate any opportunity for civil society to mobilize and oppose the Kremlin and its war."
Russia says such laws are required to protect the country from infiltration by Ukraine and Western intelligence agencies.
"The amendments are necessary to protect against the unprecedented threats that our country now faces from Ukraine and its Western sponsors," lawmaker Vasily Piskarev said when they were introduced earlier this month.
(Reporting by Jake Cordell; Editing by Mark Trevelyan)
