Former deputy prime minister Nemtsov, a fierce critic of President Vladimir Putin, was gunned down just yards from the Kremlin as he walked home with his girlfriend late on the evening of February 27, 2015.
The brazen murder in central Moscow was the most high- profile political killing in Russia since Putin rose to power some 17 years ago.
The 12-person jury ruled on the third day of deliberations that defendants Zaur Dadayev, Shadid and Anzor Gubashev, Temirlan Eskerkhanov and Khamzat Bakhayev -- all ethnic Chechens from Russia's volatile North Caucasus -- carried out the hit as part of an organised gang.
The Gubashev brothers, Eskerkhanov and Bakhayev were found guilty of helping to organise and carry out the killing.
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The jury's decision was reached by majority vote after they first failed to reach unanimous decisions on the long list of charges against the defendants at the end of ten months of hearings.
The suspects have always denied they were involved in the killing and several retracted initial confessions they said were made under torture.
The defendants are now facing lengthy jail terms, with the judge set to deliver sentencing after prosecutors set out their demands.
"In two years... They could not find the organiser and mastermind of the murder," said Nemtsov family lawyer Vadim Prokhorov.
"It's a complete fiasco."
Prokhorov said, however, that he was convinced that all of the accused, with the exception of Bakhayev, were involved.
Nemtsov's friends and family insist the evidence clearly shows that those close to Kremlin-loyal Chechen strongman Ramzan Kadyrov -- or Kadyrov himself -- were actually behind the assassination.
The Chechen leader has denied all involvement and defended some of the accused.
Investigators only named Geremeev's driver Ruslan Mukhudinov as an organiser and said he offered the suspects 15 million rubles (about $250,000 or 220,000 euros at current rates) for the murder.
Mukhudinov has since fled and is still being sought by police.
Once one of Russia's most popular politicians, liberal reformer Nemtsov was at one stage seen as a possible successor for former president Boris Yeltsin.
After initially backing Putin when he came to power, Nemtsov soon became one of his fiercest critics. But as the ex-KGB officer cracked down on dissent, Russia's opposition -- and Nemtsov along with it -- became increasingly marginal figures.
The murder and subsequent trial have strong echoes of a string of earlier high-profile assassinations in Russia, that Kremlin critics say have been left unsolved.
Most prominent was the 2006 shooting of crusading journalist Anna Politkovskaya in her Moscow apartment building.
Eventually five men -- including four members of the same Chechen family -- were found guilty of the murder, but over a decade later Politkovskaya's family and former colleagues remain convinced the masterminds have not been brought to justice.