Cardinal Matteo Zuppi Cardinal will be in the Russian capital on Wednesday and Thursday, a statement said.
"The main purpose of the initiative is to encourage humanitarian gestures, which can contribute to facilitating a solution to the current tragic situation and find ways to achieve a just peace," the statement said.
It was not clear who Zuppi would meet in Moscow.
He met Ukrainian President Volodymyr Zelenskiy and religious leaders in Kyiv on June 6.
If Zuppi, 67, meets Russian President Vladimir Putin, he would be one of the first foreigners to do so since an aborted mutiny against the Russian military at the weekend.
A Vatican source said Zuppi's trip had been at risk of being called off because of the attempted mutiny and the confusion surrounding it.
Zuppi told reporters last week he would consult with the Pope before leaving for Moscow.
Speaking of his dual visits to the two capitals, he said it was "a pattern that needs to be woven for the resolution of the conflict".
Zuppi was expected to meet with Patriarch Kirill, the head of the Russian Orthodox Church, according to the French Catholic newspaper La Croix.
Kirill is a close ally of Putin and fully backs the Russian invasion of Ukraine as a bulwark against a West he describes as decadent.
His full-throated support for the war has fractured the world's Orthodox Christian communities.
The Vatican statement's mention of "humanitarian gestures" appeared to be a reference to Kyiv's request - and the Vatican's willingness - to help with the repatriation of Ukrainian children.
Kyiv estimates almost 19,500 children have been taken to Russia or Russian-occupied Crimea since February 2022, in what it condemns as illegal deportations.
Zelenskiy has asked the Vatican to back his unconditional peace plan, which calls for restoring Ukraine's territorial integrity, the withdrawal of Russian troops and cessation of hostilities, and the restoration of Ukraine's state borders.
