The Scotland international has been part of a side to have kept six clean sheets in their last nine matches.
"Berra is the best defender in the league, for me, without a doubt," McCarthy told BBC Radio Suffolk.
"He's just outstanding, he's big and powerful and wins it in the air, he's quick, he blocks things and is good at defending corners."
Berra has impressed alongside youngster Adam Webster at the centre of Ipswich's defence this season, and McCarthy has previously said Webster will go onto play in the Premier League.
The pair played on Tuesday against Burton as Town ended a winless run of five matches and McCarthy's side travel to leaders Newcastle United on Saturday.
Former Republic of Ireland boss McCarthy said he was impressed by the signings the Magpies made following their relegation to the Championship, such as Matt Ritchie from Bournemouth and Dwight Gayle from Crystal Palace.
"They went out and got players who know the Championship, don't mind playing in the Championship, all want to be out of the Championship again and probably think they can be.
"How they dealt with it, they were good signings in the summer."
Ipswich Town's Christophe Berra is the best defender in the Championship, according to his manager Mick McCarthy.