New Zealand great Dan Carter will play for the Blues in Super Rugby, which starts next weekend.
Carter, 38, was a free agent after finishing his spell in Japan with Kobelco Steelers.
The fly-half played 112 times for New Zealand, helping them win the World Cup in 2011 and 2015.
“I’ve not played for several months so it will take me a little bit of time to get game-ready,” said Carter, who lives close to the Blues’ base in Auckland.
“Two things from the lockdown that I realised was I really enjoyed spending more time with my family and I miss rugby.”
As well as winning the World Cup twice, he has been named the IRB World Player of the Year on three occasions and, with 1,598 points for New Zealand, is the top-scoring player in international rugby.
Carter was out of contract after his Japanese club’s competition was cancelled because of the Covid-19 pandemic and he will replace utility back Stephen Perofeta, who fractured a bone in his foot during training.
Blues head coach Leon MacDonald said: “For Dan it’s not about the money. He’s here as a favour, with a desire to give back to the sport. We’re only a few minutes from his home so it works out perfectly and we’re thrilled.
“We have two designated 10s in Beauden [Barrett] and Otere [Black], and Dan will be there to help them and our other young backs. If he gets back into playing form that warrants selection, then he could help us as a utility back in midfield or full-back.”