Despite strong opposition from Ukraine, 118 parliamentarians from Council of Europe member states agreed that Russia could present a delegation, paving the way for it to participate in the election of a new secretary general for the pan-European rights body on Wednesday.
Sixty-two members of the Strasbourg-based body's parliamentary assembly (PACE) voted against the move and there were 10 abstentions following Monday's late-night debate.
Moscow representatives were stripped of their voting rights after Russia's annexation of Crimea in 2014.
Russia responded by boycotting the assembly, and has since 2017 refused to pay its 33-million-euro ($37-million) share of the annual budget of the human rights watchdog.
It had threatened to quit the body altogether if it was not allowed to take part in Wednesday's election, a move that would have prevented Russian citizens from being able to appeal to the European Court of Human Rights.
Amelie de Montchalin, France's Secretary of State for European Affairs, said "it would be dangerous... to deprive millions of citizens of access to bodies that protect their rights".
Ukraine, which has been supported by Baltic countries and Britain, had been against Russia's return to the council.
'A very bad message'
It has previously warned that reopening the door to Moscow would be the first crack in international sanctions imposed on Moscow after it annexed Crimea.
"If Russia comes back, it would send a very bad message," Ukrainian lawmaker Volodymyr Ariev, head of his country's PACE delegation, told AFP.
"Do whatever you want, annex other countries' territory, kill people in other countries -- and you will get away with everything."
He said Russia had done nothing to deserve the lifting of the sanctions.
"Its return to the assembly will mean that it has been forgiven. This is a test for Western countries: are they ready to work in earnest to protect democracy?"
But many Russian rights activists say it would be better for everyone - including Ukraine - to have Russia in the Council of Europe.
"If Russia leaves, the Council of Europe would lose the limited levers of influence it currently has," Yuri Dzhibladze, a prominent rights campaigner, told AFP.
"Over the past five years the sanctions on the Russian delegation at PACE have not had any effect on human rights violations, the rise of authoritarianism, and the Russian authorities' aggressive actions on the international arena."
The Council of Europe, which is separate from the European Union, has no binding powers but brings together around 300 lawmakers from 47 states to make recommendations on rights and democracy.
Its centrepiece is the European Court of Human Rights.
The Council's Parliamentary Assembly will on Wednesday elect a new secretary general to replace Norway's Thorbjorn Jagland.
Two candidates are in the running: Belgium's Deputy Prime Minister Didier Reynders and Croatia's Foreign and European Affairs Minister Marija Pejcinovic Buric.