The 33-year-old, normally a loose-head prop who can also play tight-head prop, will now move to Sixways in the summer and link-up with Head Coach Richard Hill who he worked under at Newport during the 2002/03 season.
Jones originally joined Quins on-loan from that spell at Newport in February 2003, before signing a full time contract at the end of the 2002/03 season. He made his debut in the Premiership fixture away to Bristol Shoguns in March 2003 and has gone on to make almost 150 top-flight appearances.
Head Coach Richard Hill believes the powerful front row, who made his international debut for Wales on their summer tour of Australia in 2007 and stands at 6ft tall and weights 18st 3lb, will make a big impact at Warriors.
"I have known Ceri for a long time and he is a consummate professional, a fantastic scrummager and a very good leader of men," said Hill.
"Ceri is an ultra consistent prop who is very durable and just keeps going and going, underlined by the number of games he has played in the Premiership and Heineken Cup. We are delighted that he will join us next season and really add to the squad we are building.
"Ceri has been a mainstay of the Harlequins team for almost a decade, a side that plays an attacking style of rugby. He has been heavily involved in that so he will fit in with the way we want him to play.
"We also need people who have experienced success at Premiership level - a league he knows inside out - as we look to the coming years. Ceri will bring us that along with the hard work and superb attitude he is renowned for.
"He will also complement the existing props we have at Sixways. Ceri has been an excellent role model for the likes of Joe Marler at Harlequins and I am sure his addition and experience will benefit players like Matt Mullan."