The 38-year-old signed for Warrington in 2002 and has played 441 times for the Super League club, winning three Challenge Cups with the Wolves.
He also played in the 2008 and 2013 World Cups for his country, representing England on 27 occasions.
“It’s been a difficult decision but one that had to be made. I think the time is right,” said Westwood.
“There’s still time to achieve some more this year too but sadly at the end of this one that will be it for me.
“It’s sad that this time has to come but it was always going to and at 38 years old I haven’t done badly.”
He continued: “I am going to be working with the backroom staff and in the office, and coaching the women’s team too. I will still be around, still be involved in the club, which will hopefully make the transition a little bit easier.”
Warrington captain Chris Hill added: “He is part of the furniture and will be sadly missed. He knows the time is right though.
“The way he has played the game for the last 20 years is going to have taken its toll. He’s done so much for the sport. Everyone knows Bennie Westwood.”