"My presence here reflects the respect of the entire free world for your people and underlines Greece's commitment to remain by your side," Mitsotakis told Zelenskiy in his first visit to the country since Russia's invasion in February 2022.
Zelenskiy and Mitsotakis visited a residential building - the site of Russian drone attack on Saturday that killed 12 people, including five children.
Mitsotakis said that during his tour sirens had sounded and they heard a big explosion as they headed towards their cars.
"I believe that this is for us the most vivid reminder that there is a real war waging here," Mitsotakis said, urging other European leaders to visit Ukraine to get a first-hand sense of the war's impact on civilians.
"You see who we're dealing with, they don't care where to hit. I know that there were victims today, I don't know all the details yet, but I know that there were killed, there were wounded," Zelenskiy said.
European Commission President Ursula von der Leyen, in a post on X, said she strongly condemned "the vile attack on Odesa" during the leaders' visit.
There was no immediate comment from Russia.
Ukraine's Black Sea port infrastructure has been a target for Russian attacks, which have stepped up since mid-July when Moscow quit a U.N.-brokered deal that allowed safe passage of Ukrainian grain shipments.
Ukraine has since launched a its own "humanitarian corridor" for ships to try to circumvent a de facto Russian blockade of Kyiv's seaborne exports via the Black Sea.
Greece, a NATO member and a traditional ally to Ukraine's bid to join the military alliance and the European Union, has offered military help to the country.
"We discussed what other means we can use to expand the security space in the Black Sea. How we can add protection to our people - both military and civilian. We need more air defence," Zelenskiy said.
Mitsotakis said that Greece would participate in a high-level Ukraine peace conference in Switzerland.
(Reporting by Iryna Nazarchuk and Renee Maltezou; Writing by Angeliki Koutantou; Editing by Toby Chopra and Alex Richardson)
