First-half goals from DJ Campbell and Daryl Murphy gave Town a cushion, and although the Addicks hit back through a Danny Haynes penalty they were unable to prevent a third successive defeat.
McCarthy was delighted with the way his side held on and said: "The self-belief comes with winning games. It doesn't come from me, it comes from within. They are professional players and it helps when you are winning, or at least putting in decent performances."
He added: "It gets a bit flaky at times and you wonder if you are going to be able to hang on. But they did and I'm pleased with them."
Ipswich had a great opportunity to score after just 16 minutes when defender Emmanuel Frimpong conceded a penalty after tripping Lee Martin. However, on-loan Campbell, in his penultimate game before going back to QPR, hit his spot-kick well wide.
Campbell then made up for that miss by taking advantage of poor Charlton defending in the 35th minute as he steered in a loose ball after more trickery from Martin. Former Manchester United youngster Martin's fierce shot was then saved by Ben Hamer but Murphy reacted quickest and buried the rebound as half-time loomed.
McCarthy said: "The two penalties opened the game up. We missed ours but it gave us an impetus to go on. We got good quality goals. DJ persisted after the miss and took his very well. They have two good centre-forwards who gave us a lot of problems but we persisted and held on."
The Addicks looked lethargic and manager Chris Powell responded during the break by replacing Frimpong with Bradley Pritchard, while Johnny Jackson went on for Danny Green. And the changes worked as Martin brought down Chris Solly with Haynes finishing emphatically from the penalty spot with his sixth goal of the campaign.
Speaking after his 100th game in charge at the Valley, Powell said: "We were duly punished. It doesn't matter if it is against a team in the lower reaches, or any team. If you are not at your full capability you will get punished and that is what happened in the first 45.
"It shows how quickly things can change in the Championship. We went on a superb run but now we have lost three in a row. We have been here before and have responded and we have to do that again."
- Sports & Recreation
- Daryl Murphy
- Emmanuel Frimpong