The South African born prop qualifies for Ireland through residency and has featured for the Ireland Wolfhounds side.
"Connacht has been my home for the last 5 years and it's great to be able to commit for another 2 years. I'm delighted to have played for Ireland Wolfhounds and I would love to make the next step and represent Ireland at Senior level but at the moment I am concentrating on being the best rugby player I can be," he said.
Anderson, 24, joins Connacht on a two-year deal from Ulster where he has spent three years.
The 6'4" 98kg Magherafelt born player was part of the Ireland U20 team that won the Grand Slam in 2007 in a side that included current Connacht players Andrew Browne, Jamie Hagan and Shane Monahan