The announcement came just three hours after their disappointing defeat against the Arizona Cardinals.
This year, the Packers have won just four games this year, and have just a three percent chance of making the NFL Play-Offs this season.
And now, the decision has been made to part ways with McCarthy, who has been with the franchise as head coach for 13 years.
McCarthy will be remembered fondly by Packers fans, having won the Super Bowl in 2010.
It was the first NFL Championship the franchise had won in 14 years.
And Packers’ president and CEO Mark Murphy explained in a statement that the poor results this year led to the decision.
“The 2018 season has not lived up to the expectations and standards of the Green Bay Packers,” he said.
“As a result, I made the difficult decision to remove Mike McCarthy of his role as head coach, effective immediately.
“Mike has been a terrific head coach and leader of the Packers for 13 seasons, during which time we experienced a great deal of success on and off the field.
“We want to thank Mike, his wife, Jessica, and the rest of the McCarthy family for all that they have done for the Packers and the Green Bay and Wisconsin communities.
“We will immediately begin the process of selecting the next head coach of the Green Bay Packers.”
McCarthy has been replaced by Joe Philbin on an interim basis.
Philbin was most recently a head coach for the Miami Dolphins from 2012-2015.
He has worked alongside McCarthy as offensive coordinator from the start of this season.
And he also worked for the Packers as offensive coordinator from 2007-2011, playing a pivotal part in the Super Bowl win.
A press conference will be held by Murphy on Monday night UK time.