No reason was given for the decision not to attend, but a Kremlin spokesperson said climate change was an "important" priority for Russia, the BBC reported.
"Unfortunately, Putin will not fly to Glasgow," Kremlin spokesman Dmitry Peskov told reporters, adding that climate change was "one of our foreign policy's most important priorities".
COP26 takes place in Scotland's largest city from October 31 to November 12.
Russia's decision is seen as a blow to efforts to get leaders to negotiate a new deal to stall rising global temperatures.
Putin has not commented on the official announcement but speaking at an international energy forum in Moscow on October 13, the Russian leader cited the coronavirus pandemic as a factor in his decision to travel.
"I am not sure yet if I will attend (COP26) in person, but I will certainly take part in it," he added.
Chinese President Xi Jinping is also unlikely to attend, though Chinese officials have reportedly not entirely ruled out a change of plans.
Earlier in October, Australian Prime Minister Scott Morrison attracted widespread criticism for suggesting he might skip the summit but he later announced that he would indeed attend.
COP26 is the biggest climate change conference since landmark talks in Paris in 2015. Some 200 countries are being asked for their plans to cut emissions by 2030.