The back row, who has impressed in recent years in the Academy set-up and Guinness A League games, was one of the star performers for England Under 20s this season as they claimed the Six Nations crown.
The 20-year-old was also involved in the England Sevens squad for the recent tournament in Hong Kong.
Director of Rugby Mike Ruddock revealed Cox was attracting interest from other top-flight clubs but has decided to remain at a club that has nurtured his development.
"We're delighted we are able to announce that outstanding prospect Matt Cox has signed a one-year deal with Warriors," he said.
"Matt has been a crucial member of the England Under 20 Grand Slam winning side this season and he has the ability to play right across the back row in all positions.
"He was already at such a young age attracting a number of other club's attention. However, his desire was to remain loyal to Warriors after receiving support and development through our Academy system. This was an important reason for him wanting to extend his stay with the club."