During the 25-minute call the day after the election, Trump told Zelenskiy he would support Ukraine, without providing details, and Musk said he would continue supplying Starlink satellites, US news website Axios reported, citing unidentified sources.
Musk owns SpaceX, which provides Starlink satellite communication services that are vital for Ukraine's defence effort, but his statements have sometimes angered Kyiv since Russia invaded its neighbour in 2022.
Zelenskiy was telling Trump how important the satellites had been for internet service during the war when Trump said Musk was with him and put the billionaire on the line, the Washington Post reported.
Trump and Musk were at Mar-a-Lago, Trump's Palm Beach residence and club, when the call took place, according to the New York Times.
Musk gave millions of dollars to support Trump's presidential campaign and made public appearances with him.
Trump has said he would offer Musk, the world's richest person, a role in his administration promoting government efficiency.
Musk did not immediately respond to a request for comment. The Trump campaign said it did not comment on private meetings.
Zelenskiy was among the first leaders to congratulate Trump, who has been critical of US military and financial support for Ukraine in its war with Russia.
Zelenskiy said in a post on social media platform X that his conversations with Trump should continue.
"We agreed to maintain close dialogue and advance our co-operation. Strong and unwavering US leadership is vital for the world and for a just peace," the Ukrainian president said.
