The 30-year-old forward has been capped 11 times and joins after a month spent at Bridgend, which followed a spell with London Welsh.
"He's signed until the end of the season but, if all goes well, there's an option to extend that," said Bristol head coach Richard Hill.
"He offers great flexibility with his background in the second row and back row. However, I see him primarily as a number five playing the middle jumper role."
