He will also need to follow through on his pledge to seek peace in eastern Ukraine, where Russian-based separatists have been fighting since 2014, amid concerns that Russian President Vladimir Putin will exploit his inexperience.
And he will need to show voters that he is as serious about tackling corruption as the exactingly moral president he plays on TV - and whose regular-guy approach Zelenskiy often echoed in his real-life campaign.
Zelenskiy's TV character "is sometimes too soft and kind," said Dmytro Razumkov, a political adviser to the President-elect. "In the reality of Ukraine, given the extent of corruption and many other things, one probably needs to be tougher. Zelenskiy will be able to do this."
Zelenskiy is both an actor and a businessman. The production company he founded, Studio Kvartal 95, is one of the most successful in Ukraine. A spokeswoman for Zelenskiy said that he was in the process of disposing of his stake in the company. Razumkov said the business had given Zelenskiy negotiating experience, which will help in his presidency.
Oleksandr Danylyuk, a former finance minister who is Zelenskiy's chief foreign policy adviser, said the new president will have much to learn. Danylyuk said the main expertise that Zelenskiy brings to the presidency involves media and communications, which would allow him to build a strategy for winning hearts and minds in the swaths of eastern Ukraine now occupied by the separatists.
"How to unite people - that's his strength," Danylyuk said. "But more specific knowledge he doesn't possess. Obviously, he will develop it. But he will rely on a team."
The make-up of Zelenskiy's governing team is still unknown and will be closely watched. As president, Zelenskiy will have the power to nominate top officials, including the foreign minister, defence minister, prosecutor general, and head of the SBU security and intelligence service.
Zelenskiy pledged to replace Poroshenko's "old team" and even look into moving the administration out of its traditional space on central Kiev's Bankova Street. He stayed out of the public eye today.
Danylyuk, described in the Ukrainian press as a potential foreign minister, said he was not interested in joining the Cabinet but rather wanted to focus on government reforms. A key factor in the make-up of the new administration, Danylyuk said, will be that it not include anyone closely tied to an oligarch - including Ihor Kolomoisky, the billionaire whose TV channel aired Zelenskiy's sitcom and gave positive coverage to his candidacy.
"There should be none of his people in government," Danylyuk said of Kolomoisky. "That must happen - right? - in order for Volodymyr Zelenskiy to be successful and really deliver on the expectations of people."
Both men have denied that Kolomoisky is behind Zelenskiy's political ambitions.
A key factor in Zelenskiy's victory, analysts said, was Ukrainians' fatigue with the war in the east. Sporadic, deadly shooting continues between the separatists and Ukrainian forces in a war that has killed about 13,000 people since 2014, according to the United Nations. Zelenskiy has said he was prepared to negotiate directly with Putin to end the war, prompting fears among some Ukrainians and Western diplomats that Zelenskiy's inexperience could prove costly in talks with the Kremlin.
Danylyuk said Zelenskiy would start by mounting an effort to improve humanitarian conditions for people living in the occupied east, such as boosting the infrastructure that residents use to cross into government-controlled territory. Zelenskiy would talk to Putin through what's known as the Normandy format, which includes the leaders of France and Germany, Danylyuk said.
"What we cannot understand is just why there is so little progress on the humanitarian elements," he said. "We're not naive, but we are positive. We are optimistic."
It's not clear how the Kremlin will adjust to a Zelenskiy presidency. The President-elect has said he will maintain Ukraine's pro-Western course. But unlike Poroshenko, Zelenskiy didn't make the struggle against Russia the centerpiece of his campaign, suggesting his presidency might take a somewhat more conciliatory tack toward Moscow.
An early litmus test will be whether Russia releases the 24 crew members of Ukrainian navy ships it captured off the coast of Crimea in November. Zelenskiy described securing the return of the crew members as a top priority.
Kremlin spokesman Dmitry Peskov questioned the legitimacy of the Ukrainian election given that Ukrainian citizens living in Russia weren't allowed to vote in Russia. Kiev cited security concerns in the decision.
"It would be premature to talk about President Putin's congratulations to Mr Zelenskiy or about opportunities for their joint work," Peskov told reporters. "Judgments can be made only on the basis of actual deeds."
