The 19-year-old winger took up the option of another year on his previous contract in May, but has now put pen to paper on a new two-year deal to keep him at Preston until the summer of 2015.
Manager Simon Grayson said: "Will was only in his first full season last year and I'm delighted with the new contract that he's signed and hopefully he will improve.
"One or two other clubs might have been sniffing around and we wanted him tied down. He'll now be looking to improve on the performances that he put in for the club last year."
Hayhurst added: "I'm very happy. I wanted it sorted before I went away with Ireland (to Serbia).
"I was itching to get back. Every day I was thinking about signing and starting the season with Preston, so after getting it done I'm very much looking forward to the new season."
Hayhurst made his debut at the end of the 2011/12 season and scored his first goal for the club at Swindon in February in Grayson's first game as manager.
The Republic of Ireland Under-19s international is the second academy product to agree a new deal this summer following Bailey Wright.