The Queensland Reds pair, along with Israel Folau, will be making their first appearances for the Wallabies when they meet the tourists in the first Test of the series in Brisbane at the weekend.
While they may lack experience on the international stage, Mowen is certain that Lealiifano will make an impression on the Lions.
"This game will suit Christian perfectly. He's a massive pressure player. He's done it time and time again for the Brumbies," said Mowen. "If there's a pressure shot to be taken, he's the guy you want taking it because he always puts it through. I don't think he's ever missed a pressure shot, and I think that says a lot about him as a bloke.
"He's a guy who wants to be challenged in those hard environments and obviously Saturday night's going to be exactly that. I know from playing a lot of footy with him - as does Adam Ashley-Cooper, who'll pair up with him [in midfield] - that he's the guy you want in those situations.
"He's a great attacker and a great defender. People were probably questioning whether he could go on with his form from last year after he was halted by a big injury but he's shown this year that he's gone to the next level. I think that says loads about his character."
The first Test gets underway at 11.05am on Saturday.