Pearson was upset by referee Darren Deadman after he decided to red card Matty James and failed to see what appeared to be a foul on goalkeeper Kasper Schmeichel for Charlton's winning goal.
The Leicester boss has subsequently been charged by the FA and has until Friday to challenge it.
"The FA has charged Leicester City manager Nigel Pearson for misconduct under its Rule E3," read a statement on the FA's official website.
"It is alleged the Leicester City manager's language and/or behaviour following the end of his side's fixture at Charlton Athletic on 31 August 2013 amounted to improper conduct.
"Pearson has until 6pm on 6 September 2013 to respond to the charge."