Jarvis made his international debut last season in a friendly against Ghana at Wembley after a string of fine performances, only for his standard of play to dip during the early part of the current campaign.
But he impressed McCarthy during the defeats against Manchester United at Old Trafford and then Stoke at Molineux on Saturday.
Potters manager Tony Pulis replaced makeshift right-back Jonathan Woodgate after only 20 minutes at the weekend after he had been given a roasting by Jarvis.
McCarthy said: “I think Jarvo has been excellent, certainly in the last two games.
“Against Manchester United, he was terrific and the reality is he caused havoc for 20 minutes against Stoke.
“He got ‘assaulted’ on one occasion and then got tripped for the penalty.
“Tony (Pulis) had to take Woodgate off.
“Jarvo was excellent and it is great to see him back at his best.”
“It means he must be back to the form which earned him an England call because he is back to his best – and his best was when England were wanting to give him a cap.
“We’ve had performances like that from different players. We could do with them all at their best tomorrow night against Norwich.”
McCarthy is aware of the need for his team to start keeping clean sheets after none in 13 games.
He said: “I’m concerned about everything but if you shore it up and don’t concede then you are certain of a point.
“We’ve not been able to do that for a while. A clean sheet would be fantastic.”
Meanwhile 10th place Norwich have no new injury concerns ahead of tonight’s visit to Wolves.
On-loan Manchester United defender Ritchie de Laet (back) is expected to return to training this week but is unlikely to feature.
Former Everton striker James Vaughan is on course for a return in the new year from his knee problem, along with centre-back Elliott Ward (knee).
Norwich are laying on 22 free coaches for their fans and Lambert expects the travelling support will give a boost to his team.
“It’s a great idea,” Lambert said.
“The crowd will be great, it will add to the atmosphere and hopefully we will be able to win for them.
“Any points we can get away from home are crucial.”