UEFA’s Control, Ethics and Disciplinary Body issued the warning after investigating a report of an object being thrown towards the pitch during the game at the National Football Stadium at Windsor Park in Belfast on June 13, 2015.
European football’s governing body launched the investigation after a firework was thrown from a section of the ground where Romanian supporters were sitting.
The decision by UEFA’s Control, Ethics and Disciplinary Body is a warning to the Irish FA that it should ensure similar incidents are avoided in the future.
Irish FA Chief Executive Patrick Nelson said: “The Irish FA is satisfied with this decision.
“It proves Northern Ireland fans were not responsible for the incident, and it upholds the good reputation of our fans.
“We will take heed of the warning from UEFA and endeavour to ensure such an incident is not repeated at the National Football Stadium.”