The monumental artwork, which was personally approved by Russian President Vladimir Putin, is being shipped to the city's Saint Sava temple, the largest Orthodox church in the Balkans.
Serbian Foreign Minister Ivica Dacic said it "will once again show our unity and togetherness with the Russian people and the Russian state."
Construction on the 1,230 square metre mosaic began in 1985 and it has been partly funded by the Russian gas giant Gazprom.
Mr Dacic added: "We must cherish eternal brotherhood and friendship with the Russian federation in these turbulent times when we need friends most of all."
One section of the £3.3 million work of art, featuring the head of Jesus Christ, was exhibited for people attending a service at the church.
Serbia has begun the formal process of seeking to join the European Union but under the current government it has been turning more and more to Russia, its traditional ally.