Wanderers went 1-0 up thanks to Kevin Foley's goal five minutes into the second half before efforts from Darren Bent and Danny Welbeck put Sunderland in the driving seat.
Stephen Hunt swiftly drew things level having come off the bench, though, and another substitute, Sylvan Ebanks-Blake, lashed home a dramatic winner with a minute remaining.
It was the first time the midlands club had picked up any points since the end of October, and McCarthy was delighted to see his players' dedication to the cause rewarded.
"I take a huge sense of pride from the fact that every time the team goes out I get every last drop out of them in terms of effort and application," McCarthy said.
"We maybe could do with a bit more quality at times when it comes to that final pass or final ball, but we never ever lack in effort, heart or belief. They give me everything."
Source: PA
Source: PA