The Polish goalkeeper has joined from Notts County and was handed his debut in Tuesday night’s pre-season friendly draw with Premier League West Ham United.
The 27-year-old, who has previously spent time at Portman Road on loan in 2009, impressed on his bow and looks ready to compete with Dean Gerken for the number one jersey.
McCarthy said of the new arrival: “There’s no transfer fee – there’s a clause in it if we get promoted, a sell-on clause, but there wasn’t a fee.
“We’ve been trying to get him for a long time. And we’ve all seen why I’ve tried to get him because he played well tonight.”
Pressed on whether Bialkowski is now in contention for a starting berth on the opening day of the new season, McCarthy added: “No, Dean Gerken is number one – as Loachy (Scott Loach) was last year.
“We saw what happened there though didn’t we? Dean Gerken played 40 games.
“I’ve said to Gerks, as well as he’s done and as much as I love him, if the other fella is better, then he knows what happens – even if the other fella has got the number 33 on his back.”
Meanwhile, McCarthy has revealed that he is still exploring the option of moving Freddie Veseli out of the club, with the young centre-half in need of regular football.
He added: “He’s one of my players. While he’s here I’ll continue to use him but if I can get a deal for him somewhere, I will.”