Ukrainian President Volodymyr Zelenskiy and Serbian President Aleksandar Vucic held talks in Athens on Tuesday which both leaders described as "good" and "open".
Serbia has repeatedly condemned Russia's invasion of Ukraine at the United Nations and other international forums but has not imposed sanctions on Moscow.
It also maintains trade and military cooperation with its traditional Slavic and Orthodox Christian ally, while seeking to join the European Union.
In April, leaked Pentagon documents showed Serbia had agreed to supply arms and ammunition to Kyiv, or sent them to Ukraine. Vucic said Serbia had never sold weapons or ammunition to Ukraine or Russia although Serbian arms might have reached the battlefield via third countries.
"An open, honest, and fruitful meeting with the President of Serbia," Zelenskiy wrote on the Telegram messaging app under a photograph of the two leaders shaking hands.
He gave few details but added: "Good conversation on respect for the UN Charter and the inviolability of borders...On our nations' shared future in the common European home. On developing our relations, that is in our mutual interest."
In a post on Instagram, Vucic said he had had a "good and open" conversation with Zelenskiy on issues including the territorial integrity of both countries.
Ukraine does not recognise Kosovo, which declared independence from Serbia in 2008. Belgrade, meanwhile, does not recognise Russia's annexation of parts of Ukraine which it occupies.
"We have tackled developments in Ukraine and Kosovo and I have stressed once again that Serbia respects the territorial integrity of Ukraine," Vucic wrote.
Both leaders, who were in Athens as Greece hosts a meeting of Balkan leaders, issued words of support for each other's countries' bids to join the EU.
