David McGoldrick and Luke Chambers took advantage of poor defending to head home from two first-half corners, before McGoldrick deservedly sealed the points with his second on 51 minutes.
Ipswich could have even had more with Frank Nouble seeing a goal chalked off for offside after Daryl Murphy was denied.
The win extended Town's unbeaten run to six games and at the final whistle moved them up to fifth in the table.
That is a far cry from 14 months ago when McCarthy took over with the club rock bottom of the division.
After just about steering them to safety last term, McCarthy has the Town fans believing in a side that have lost only to high-fliers Leicester and Burnley since September.
And while he was able to deliver more good news after the win at the Keepmoat Stadium - with Manchester United loanee Ryan Tunnicliffe set to extend his stay - McCarthy warned the club about getting ahead of themselves.
"Recent performances have been good but this league is so bonkers," he said.
"You can have that good run and get in the top three but then you can lose three easily on the bounce.
"They (Doncaster) beat Leicester here and QPR here - that's the league."
McCarthy added: "Tiny detail wins and loses games and tiny details won us the game today. Two corners and they're not quite marked properly.
"I'm sure (Doncaster boss) Paul Dickov will be going mad at that. We want to keep this run going but we go to Bournemouth next and they'll want to give us a slap.
"You still have to go there and win the battles and do all the tough little jobs.
"It's glib and too simple to think differently."
McGoldrick was the outstanding player on show as his double increased his season's tally to 11 goals.
He was instrumental too in winning the corner for Chambers' goal, playing a clever one-two with Tunnicliffe.
"He's been terrific, McCarthy said. "His all-round contribution - he's not just a goalscorer he works back in defence too.
"He's a good player and a good bloke."
McCarthy also revealed he had already spoken to United boss David Moyes about extending Tunnicliffe's loan until the end of the season.
"I'm pleased with him," he said. "He's fitted in with us great. I want him to stay.
"I've spoken to David and that is what will happen barring an accident."
Rovers boss Dickov lamented the defensive mistakes that cost them a 2-0 half-time deficit.
"We can work on tactics and formations but you can't legislate for two player switching off at a set-piece," he said.
"Especially against a big, physical team. You can't expect to come back from that.
"It was far too easy. Far too easy."
Dickov believes a long injury list is starting to bite after a loss that leaves them just a place above the drop zone.
Doncaster were without nine first-team players and most of their preferred defensive line.
"You have to deal with it," said Dickov, who has now seen his side win once in 12 games.
"I've been loath to blame the injuries in recent weeks but it is taking its toll.
"We want to stay in this division. I still believe we will do that comfortably."