The 19-year-old came through the club's academy and made his first-team debut at the start of last season.
Tongue has taken 30 County Championship wickets in 2017 at an average of 24.26.
"We are absolutely delighted to be securing the services of one of our best young players," said director of cricket Steve Rhodes.
"He is one of the brightest young fast bowling talents around the country. He is a guy who loves Worcestershire, enjoys playing at Worcester and wants to do well for Worcestershire."
Teenage paceman Josh Tongue has signed a new four-year contract with Worcestershire, keeping him at New Road until the end of the 2021 season.