The 33 year old has a full time community role, believed to be in Wakefield, so will join Keighley on match terms.
Demetriou told the League Express: “I’ve been speaking to Semi for a while – I’m good mates with him and have been for a while, since we signed at Wakefield in 2003.
“He’s at the age where he needs to start thinking about a career path after rugby, and a club has offered him the opportunity of a full time job. He texted me a few days ago and asked if we could offer him anything here, and i told him that we had match terms available.”
The winger has been proven as a prolific try scorer for both Wakefield and Bradford Bulls, where he scored 85 tries in 35 appearances, and Demetriou believes he will be a great asset to the Cougars.
He added: “He will be fantastic for us, he’s an absolute weapon in attack. He’s very aggressive and strong, and strong defensively.”
Tadulala is known for playing in the wing position for his past Super League clubs but the Keighley coach has said that he will probably feature in the centres for Cougars as he does when playing International rugby for Fiji.