Finland Prime Minister Sanna Marin. AP
Marin described Russia's war in Ukraine as a "turning point" for Europe, during a press conference with Ukrainian Prime Minister Denys Shmyhal.
The conflict, she said, has "changed the European security environment profoundly, as well as our perception of Russia".
"Trust is lost for generations," Marin said.
Her visit comes after Finland and neighbouring Sweden filed historic applications to join NATO in the wake of Russia's invasion of Ukraine on February 24.
Marin during her trip visited Irpin and Bucha, towns on the outskirts of the Ukrainian capital where Russian troops have been accused of killing civilians.
She also met Ukrainian President Volodymyr Zelensky and the Chairman of Ukraine's parliament Ruslan Stefanchuk.
In a statement following the visit, she said it was "important for the European Union to be united, bold and determined in the face of Russia's invasion."
She also backed Kyiv's closer integration with Brussels, saying it was "important to create concrete steps for Ukraine to become an EU member state."