The 29-year-old previously played in England with Premiership side Saracens on a short-term deal in 2016-17.
He made his international debut against Tonga in 2012 and played 25 times for Samoa, his last cap coming against against England at Twickenham in 2017.
Born and raised in Auckland, Lemalu was a leading light at De La Salle College in the south of the city.
He has spent the majority of his career in Japan with the Munakata Sanix Blues in the ‘Top League’ and latterly with the Sunwolves in Super Rugby.
He joins Carnegie from New Zealand Mitre 10 Champions Auckland having helped them to their first Premiership since 2007 – and 17th in total – with a dramatic 40-33 extra-time victory over Canterbury at Eden Park.
Lemalu said: “I am looking forward to taking up this great opportunity to work alongside [director of rugby] Chris Stirling, the Carnegie management, coaching staff and my new team-mates.
“Thank you to everyone involved in making the move possible.
“I am thrilled to be calling Yorkshire Carnegie Rugby my new home.”
Stirling reckons his latest recruit will prove a key addition to Carnegie’s pack.
He said: “We are delighted to have signed a player of the quality of Fa’atiga Lemalu.
“He has arrived in great form having just helped Auckland to win the Premiership in New Zealand and has a fantastic record in Japan earlier in his career.
“He will be a huge presence in our forward pack and someone who will add a great deal to our Championship squad as a senior player.”
Carnegie are four points adrift at the bottom of the Championship table having won only one of their opening nine games, but began their Championship Cup campaign in impressive style last weekend with a 38-19 victory over fourth-placed Nottingham, avenging September’s 36-17 home league defeat, at Huddersfield YMCA.
They visit Coventry in the same competition on Saturday.