Zaha failed to make an impression on David Moyes last year before a temporary switch to Cardiff City and has now been deemed surplus to requirements by Louis van Gaal.
Goal understands the deal was agreed on Wednesday evening following Warnock's appointment as Tony Pulis's successor at Selhurst Park and the new manager is delighted to the imminent deal.
"I think Wilfried needs us, like we need Wilfried," he added. "He's been at a big club like Manchester United and I think he's got a bit lost. I spoke to him last night for a good hour.
"Wilfried's always had a great attitude for me. He wants to learn, he wants to do extra training and he wants to improve.
"The fans [at Palace] love him and that's what he needs. He needs an arm around him. I hope that we can get the best out of him for the next 12 months.
"I think we're going to be really busy [in the rest of the window]. We've got to try and get some targets over the line. It's not going to be easy but it never is."