Since leaving New Zealand, Messam has played for the Toshiba Brave Lupus in Japan and he spent the last two seasons alongside Savea with French club Toulon.
Messam has 85 provincial caps over his 12 seasons for Waikato, who open their season at home to Wellington on September 12. He also made 179 appearances for the Chiefs, winning two titles.
Waikato coach Andrew Strawbridge was excited to have Messam onboard.
"Messam is a very talented and vastly experienced player, who can play a range of positions in the loose forwards. He is another one of these players that cares deeply about the jersey, his teammates and is well respected by the province, so we are very fortunate to have him back in the colours."