Douglas, who has won 43 caps for his country, will move to Warriors in the summer on a two-year deal after a successful playing spell in the Top 14.
The 30-year-old tighthead began his career at Harlequins, before moving back north to the newly-formed Border Reivers in 2002.
The Edinburgh born front row, who has also represented Scottish Schools, Scottish Districts and Scotland at Under 16, Under 18, Under 19 and Under 21 levels, won his first cap for Scotland in the 37-10 win against Romania in November 2002. He played in all three of Scotland's victories in the 2002 tour of North America.
In 2003, Douglas scored his first try for Scotland in the 30-22 victory over Wales. He toured South Africa with Scotland in 2003 and his outstanding work-rate earned him recognition on the 2004 tour of Australia.
After the Borders were disbanded in 2007, Douglas was signed by the Llanelli Scarlets as the Welsh region attempted to bolster their front row before making the move to France.
"Our recruitment plans for next season are moving on at considerably pace and that is highlighted by the announcement today that we have signed Scotland international tighthead prop Bruce Douglas," said Mike Ruddock.
"Bruce has won 43 caps for Scotland and he brings with him that experience and also a huge work-rate, for example when he played for Montpellier against the Warriors this season he made 15 tackles in the game.
"That just shows what an effective contribution he can make to the team, not only at the set piece but in broken play.
"For a prop he is still a relatively young man at 30 and we believe working with Tony Windo he will continue to develop into the prime years in his career."
Giant prop Douglas, whose international CV includes victories against South Africa, England, France, revealed his excitement about joining the Warriors from next season.
"I'm really looking forward to the move to Worcester and this is a great opportunity for me to come back and play in England," said Douglas, who is 5ft 11in and 17st 4lb.
"I have played at Sixways on a number of occasions, most recently for Montpellier this season, and so I know how good the set-up is and how the club has grown. I feel I am joining at the right time and I'm excited about the future."
