After Everton defender Ashley Williams clashed with Lyon's Anthony Lopes, a fan in the Everton end - who was holding a child - appeared to strike the goalkeeper on the forehead.
Everton confirmed they would ban the supporter involved in the incident, but a UEFA charge has led to the Premier League club being issued with a fine.
The UEFA Control, Ethics and Disciplinary Body confirmed on Wednesday that Everton have been ordered to pay €30,000 due to "aggressions by supporters against players".
A statement from Everton released at the time said: "Club officials have reviewed the footage of an incident that occurred in the 64th minute of the game against Olympique Lyonnais where supporters towards the front of the lower Gwladys Street End became involved in a confrontation between players.
"We have identified one individual whom action will now be taken against. This will include a ban from attending future Everton fixtures and the club registering a formal complaint with Merseyside Police."