Maher, who turns 20 in July, signed a five-year deal with last season's Eredivisie runners-up and will complete his medical on Monday.
"We have been looking at signing him for a long time," PSV's technical director Marcel Brands told the club's website. "With him we have a very talented Dutch player who fits the philosophy of PSV."
Maher, who was born in Morocco, joined AZ in 2004 and made his senior debut in 2010.
He scored 22 goals in 94 club appearances and has four senior caps for the Dutch national team.