Mykolenko made his debut in the Ukrainian Premier League for Dynamo Kyiv on 20 August 2017, playing in a winning match against Stal Kamianske.

[4] On 25 October 2018, Mykolenko made his debut in the UEFA Europa League, starting in Dynamo's 2–1 victory over Rennes at the Roazhon Park.

[9] On 3 March 2022, as a gesture of goodwill, Mykolenko was named Everton captain for an FA Cup Fifth round match against Boreham Wood due to the Russian invasion of Ukraine between his country and Russia.

[11] On 8 May, Mykolenko scored his first goal for Everton, a stunning volley from 25 yards in a 2–1 away victory against Leicester City in a Premier League fixture.

[13] Still eligible for youth football, Mykolenko just missed out on winning the 2019 FIFA U-20 World Cup but was named to the eventual winner Ukraine squad for the tournament, but had to be withdrawn from the competition a few days later due to injury.