The Football Association will not take any action against Manchester United boss Sir Alex Ferguson over his gesture at the Madjeski Stadium on Saturday.
Ferguson served a two-match ban less than four weeks ago
Reading fans claimed that Ferguson aimed an 'up yours' sign at them during United's 2-0 Premier League victory.
But Ferguson said: "All I was doing was expressing my relief at winning one of our hardest games of the season."
The incident came after Cristiano Ronaldo scored United's second goal deep into added time.
Ferguson had already clashed with Reading assistant boss Wally Downes after the fourth official indicated four more minutes were to be played.
When Ronaldo sealed the win, Ferguson appeared to respond to home fans who had voiced their disapproval as he complained about the amount of stoppage time.
Ferguson served a two-game touchline ban earlier this season after being found guilty of using foul and abusive language towards referee Mark Clattenburg during a defeat by Bolton.