The winger’s extension will secure his future with Widnes until at least the end of 2018 season.
Ah Van has made a career total of 163 appearances.
“When the Club approached me to re-sign I was only ever really going to sign here,” he said.
“During my four years here I have come to think of Widnes as home. The team is constantly improving, the Club is getting stronger and the work we do in the community gets better year on year and I am proud to be part of that.
“I want to thank the fans for their support over the last couple of years and I look forward to the future in black and white.”
Widnes head coach Denis Betts described Ah Van as a “strong and well thought of member of the squad”.
“His try scoring record speaks for itself,” he said.
“I have said before what a great acquisition he has been for the Club and look forward to working with him in the coming seasons.
“Pat contributes so much on the field but is also invaluable for his outstanding contributions supporting our off field community work. He is a real club man.”