The midfielder scored his first goal since moving to Palace in the last transfer window with a looping header from Yannick Bolasie's cross in the 11th minute at Selhurst Park.
Peter Crouch levelled proceedings just two minutes later and, despite McArthur twice going close either side of half-time, the match finished 1-1.
Former Wigan Athletic man McArthur drew praise for his performance, but manager Warnock feels it was a mere continuation of his recent form.
"I think he's had six or seven [performances] like that," Warnock said. "At Everton he was fantastic.
"I think he compliments the set-up here and gives Yannick more freedom and Wilfried [Zaha]. He gets into the box as well as defending."
McArthur's goal was just his second of the 2014-15 campaign, with his last coming back in August for Wigan.
Warnock has now encouraged the 27-year-old to get among the goals more, and stated that he shared a joke with the Scotland international about his lack of goals in the build-up to the game.
"It was great to see McArthur on the scoresheet. He needs to score more - him and Joe Ledley," he added.
"Yannick and Wilfried and Jason [Puncheon] have to create things so we need more goals from other areas. It was good to see that today.
"I've been ribbing him about not scoring. I asked him if he'd scored this year and he said 'yeah once for Wigan'. So he's been due one. It's good to see that, it won't do him any harm."
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