Rory Kostjasyn, 29, makes the move after stints at the Melbourne Storm and North Queensland Cowboys, the latter with whom he won the NRL premiership in 2015.
Knights coach Nathan Brown pointed to Kostjasyn’s experience at two of the NRL’s more successful clubs as potentially being crucial at Newcastle.
He said: “We are pleased we can bring Rory back to the region after a number of years away.
“He is a natural football player who knows how to prepare and knows how to win.
“Rory joins the club after playing in two successful systems at the Storm and Cowboys.
“He will provide strong leadership and be able to educate our young side.”
Kostjasyn has made 126 appearances during his NRL career, and joins a Knights outfit who won just one game in 2016.