Pellegrini was incensed and at the final whistle refused to shake hands with Chelsea boss Jose Mourinho, who celebrated the goal with supporters behind the visitors' dugout.
Pellegrini said: "I didn't shake hands. I didn't want to shake hands."
Mourinho had no complaints with Pellegrini and insisted he entered the crowd to share his joy with his son, who has a season ticket.
Jose Mourinho: "I don't feel it is a lack of respect.
"If he was sad because of the result, I understand. If he was sad thinking that I was doing something wrong by going to celebrate there, I accept that too. No problem.
"Chelsea is guilty. They have to give my kid tickets behind my dugout."
Source: Manchester City MAD