Worrall, 27, will join Vale, subject to Football League approval, after leaving Millwall by mutual consent.
The former Bury and Southend midfielder made 41 appearances last season to help the Lions win promotion to the Championship - the fifth of his career.
"He's a very high energy player as we know and his experience speaks for itself," manager Michael Brown said.
Worrall is League Two side Port Vale's 17th signing of a busy summer transfer window.
Find all the latest football transfers on our dedicated page.
Port Vale have signed midfielder David Worrall on two-year contract following his release by Millwall.