The 32-year-old completed a medical on Wednesday, and has penned a deal that will see him stay with the Scottish Premiership outfit until the end of the season.
Djemba-Djemba had most recently been with Serbian side Partizan, but he was deemed surplus to requirements and had his contract cancelled in December.
St Mirren have acted swiftly to tie up a deal for the Cameroon international, and he adds to the permanent signing of Gregg Wylde and loan deals for Aberdeen's Josh Magennis and Newcastle United's Adam Campbell, who all joined in the January transfer window.
He has been capped on 24 occasions by Cameroon, and collected a winner's medal at the 2002 Africa Cup of Nations as well as playing at the FIFA World Cup in South Korea and Japan in the same year.
