"At the Christ the Savior Cathedral in Moscow Nils Ušakovs will be presented with the International Public Orthodox Peoples Unity Award," a statement by Riga City Council said.
"The mayor of Riga is being awarded the prize for his work in strengthening Christian principles within society," the statement continued without specifying precisely which of the mayor's activities running the municpality had contributed to "strengthening Christian principles."
Ušakovs was awarded alongside various high-ranking members of the Orthodox clergy.
His particular award was founded in 2001 and is given annually to politicians, religious and public figures who have made "a major contribution to the Orthodox peoples' spiritual and cultural unity.", as well as promoting "economic and political relations" between Orthodox peoples.
After the ceremony at which the mayor received the prize of 10,000 US Dollars, he said he would donate the money towards the renovation of an Orthodox chapel, St Nikolai's, in Riga's Spikeri district.
Patriarch Kirill, a strong supporter of Russian President Vladimir Putin, is a controversial figure. A planned visit by Kirill to Latvia last year was postponed as tensions between the two countries rose as a result of Russia's aggression in Ukraine.
Ušakovs on Thursday pre-empted criticism of the latest of his frequent visits to Moscow by saying he was trying to lay the groundwork for a resumption of full economic ties between Russia and Latvia if and when the conflict in Ukraine is resolved.
Ušakovs' Harmony party, which draws most of its support from Latvia's large Russian minority has a long-standing co-operation agreement with Vladimir Putin's United Russia party, which Ušakovs has consistently defended.