During United's 1-0 win against Southampton, Mourinho stepped onto the pitch in an effort to make a point to one of his players, but the gesture was not welcomed by the officials.
After being alerted to Mourinho's encroachment by the fourth official, the referee promptly dismissed the Portuguese, who cut a frustrated figure as he left to take a seat elsewhere.
However, the FA has regarded the incident as a minor infringement, and Mourinho will not receive a fine or touchline ban for upcoming matches.
Mourinho had previously claimed that he was unaware as to why he had been forced to leave to the stands on the south coast.
United currently sit in second place in the Premier League table after half-a-dozen matches.