Mourinho was pictured murmuring to a camera in Portuguese, and he may face a ban if it appears that his language was offensive, insulting or abusive.
Mourinho is no stranger to FA fines and punishments.
In January 2005, Mourinho was fined £5,000 for accusing Manchester United of cheating after the first leg of their League Cup semi-final.
Despite not being an FA fine, two months later he was fined £8,900 and handed a two-match ban by UEFA after Chelsea's 2-1 loss at Barcelona when he claimed he saw then-Barca boss Frank Rijkaard speaking to referee Anders Frisk.
In addition, in August 2005 the former Real Madrid manager was handed a £75,000 fine, reduced from £200,000, for his part in Ashley Cole's controversial transfer from Arsenal to Chelsea.
Mourinho's second spell at Stamford Bridge was no different, with the 'Special One' failing ot have the best relationship with England's governing body.
In October 2013, he was fined £8,000 after being sent off by referee Anthony Taylor in Chelsea's 4-1 win over Cardiff, while a month later he was fined £8,000 again after being sent to the stands by referee Chris Foy during a Chelsea loss at Aston Villa.
Mourinho was fined £10,000 for sarcasm towards referee Mike Dean after Sunderland beat Manchester United at Old Trafford.
Mourinho was also fined £25,000 for complaining of a "clear campaign" against Chelsea after Cesc Fabregas was denied a penalty at Southampton.
In October 2015, he was fined £50,000 and handed a one-match ban after saying referees were "afraid" to give Chelsea penalties.
Believe it or not, his behavior has not changed at Old Trafford.
The 55-year-old was charged three times in the space of six weeks by the FA in late 2016
He was fined £50,000 for comments made about referee Anthony Taylor ahead of Manchester United's goalless draw at Liverpool before being given a one-match touchline ban and £8,000 fine following an incident with Mark Clattenburg during United's draw with Burnley.
The Portuguese was also banned for one game and fined £16,000 after being sent to the stands by Jon Moss for kicking a water bottle against West Ham.
He may now face charges after his comments after their victory against Newcastle.