The 28-year old joins from New Zealand side Manawatu and won his first two caps with the Samoan national team during the summer, playing twice against Tonga.
Tuimauga will link up with the Connacht squad in the coming weeks with a view to being available for selection later in 2021.
Commenting on the signing, the province’s head coach Andy Friend said: “It’s no secret we’ve been exploring further options at loosehead following Denis Buckley’s long-term injury, so we are really pleased to welcome Tietie to Connacht.
“We now have strong cover across all of our front row, which is a good place to be, and with Tietie’s experience he’ll offer us something different.
“We now have a pro squad of 44 plus a number of integrated Academy players, so I’m really pleased with the group we have assembled.
“Our sole focus now is on building on last week’s win when we face the Dragons on Saturday.”
