The 27-year-old, who has won 35 Test caps and is primarily a scrum-half but can also play on the wing, moves to Sixways following a spell with South Africa's Sevens team.
"I can't wait to play in Aviva Premiership Rugby and am relishing the challenge that lies ahead," Hougaard told the official Warriors website.
"After speaking with Dean (Ryan, Warriors director of rugby) and close friend Wynand Olivier, Worcester sounds like a fantastic place for any top end athlete to be.
"Hopefully I can add some experience to the side and we can start pushing our way up the table in this last block of games."
Worcester are currently only two points above the Aviva Premiership's bottom club London Irish having lost their last eight games.
Ryan said: "Francois is a livewire scrum-half with enormous experience at the top level in South Africa.
"His signing is a statement of intent of where we are heading as a club and we are genuinely excited about what he can bring to the table."
Hougaard began his career at Western Province before moving to Pretoria to play for Super Rugby side the Bulls.
He is set to make his Worcester debut when Sale Sharks visit Sixways on Saturday.