The right-back, brought to Selhurst Park from Liverpool this summer, has settled well to life in south London.
And Warnock thinks Kelly is good enough to play at right-back for the Three Lions.
"I don't see many better right-backs in the country than Martin if I'm honest," Warnock told reporters.
"I think when you at the international scene I think Martin was good enough to play last week at right-back.
"I think Martin can fit in. I think he fitted in as if he'd been there all the time at right-sided centre-half and it's great to have players like that. Wherever I play him I think he'll have a decent game."
Arsenal defender Calum Chambers has filled the right-back slot for England in their last two Euro 2016 qualifiers and Warnock's implication is that Palace defender Kelly can challenge the 19-year-old for the position.
Kelly, meanwhile, spent seven years at Liverpool but has also started well at Crystal Palace.