The national exit poll showed Zelenskiy had won 73 percent of the vote with Poroshenko winning just 25 percent, a stunning defeat for Poroshenko, long seen as a favorite of western powers for his anti-Russian views.
Poroshenko admitted defeat by stating"'Never give up' – they tell me now when I see the results of the exit polls. And the results are clear and give me grounds to call my opponent and congratulate him on his victory," Poroshenko said at the press center of his campaign headquarters.
If the poll is right, Zelenskiy, who plays a fictitious president in a popular TV series, will now take over the leadership of Ukraine.
Zelenskiy, whose victory fits a pattern of anti-establishment figures unseating incumbents in Europe and further afield, has promised to end the war in the eastern Donbass region and to root out corruption amid widespread dismay over rising prices and falling living standards.
The 41-year-old Zelenskiy’s unorthodox campaign traded on the character he plays in the TV show, a scrupulously honest schoolteacher who becomes president by accident after an expletive-ridden rant about corruption goes viral.
Zelenskiy faces scrutiny over his ties to a powerful oligarch called Ihor Kolomoisky, whose TV channel broadcasts his shows. Poroshenko also tried to portray him as a Moscow stooge.
Investors are seeking reassurances that whoever wins will accelerate reforms needed to attract foreign investment.
"Since there is complete uncertainty about the economic policy of the person who will become president we simply don't know what is going to happen and that worries the financial community," said Serhiy Fursa, an investment banker at Dragon Capital in Kiev.
"We need to see what the first decisions are, the first appointments. We probably won't understand how big these risks are earlier than June. Perhaps nothing will change."
Voter Egor Binkevych wants a candidate to at least try to tackle the issue of corruption. “More than anything I would like for the structure of our country to change, the whole system,” he said.