McArthur, 26, was called away from the national side's Mar Hall training base on Monday after Wigan accepted a £7m offer for his services and, after swiftly completing the formalities, the deal was done. The move is expected to earn £700,000 for his former club Hamilton Academical.
"It was a bit stressful, but these things can happen in football," he said. "I'm just delighted that it is all done now and my future has been sorted. It's great to be a Crystal Palace player."