Radosław Sikorski visited the Ukrainian capital on Friday, news outlets reported.
It was his first trip after being reappointed as Poland's foreign minister.
Sikorski addressed an event to mark Ukraine's Diplomatic Service Day, paying tribute to President Volodymyr Zelensky and his decision to stay in Kyiv amid the Russian invasion, acording to officials.
The Polish foreign minister compared Zelensky to UK's World War II-era Prime Minister Winston Churchill and his leadership in the allied war effort against Nazi Germany.
Sikorski then held talks with Ukraine's top diplomat Dmytro Kuleba, Polish state news agency PAP reported.
At a joint news conference afterwards, the Polish foreign minister said that "Poland wants Ukraine to win and Russia to lose" the war, regardless of which party is in power in Warsaw.
Sikorski also congratulated Ukraine on the upcoming launch of accession talks with the European Union.
He said Poland wanted to see Ukraine, "in its internationally recognised borders, join the EU by the end of the decade."
The Polish and Ukrainian foreign ministers also said that "steps will be taken" to resolve the blockade of the Polish-Ukrainian border, caused by a month-long protest by Polish hauliers.
Polish truckers have been blocking checkpoints on the border with Ukraine, demanding that the European Union reinstate permits for Ukrainian transport companies entering the bloc.
Sikorski and Kuleba said that their talks would "help find ways to resolve" the issue, as well as matters to do with the export of Ukraine's agrifood products to Poland, the PAP news agency reported.
Sikorski stated: "We need to restore the conditions for fair competition in trade between the two countries so that everyone benefits."
Poland's top diplomat was then hosted by Zelensky, according to news outlets.
During the conversation with Ukraine's president, Sikorski "expressed strong will to support Ukraine, both economically and militarily, and also presented new proposals for bilateral cooperation," officials said.
Zelensky expressed gratitude for Poland's support for his country, and the two discussed further defence cooperation and bilateral relations, among other topics.
At a press briefing, Poland's top diplomat paid tribute to Ukraine's war effort against the Russian invasion, describing Ukraine as an "inspiration for Poland and for the entire Europe," the Polish rp.pl website reported.
In the evening, Sikorski also held talks with Ukraine's Prime Minister Denys Shmyhal, according to officials.
Friday is day 667 of Russia’s war on Ukraine.
Russia invaded Ukraine on February 24, 2022, launching the largest military campaign in Europe since World War II.
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Source: PAP, rp.pl