Northampton sign Samoa's Autagavaia
Fa'atoina Autagavaia (L) of Samoa dodges a tackle by Tomohiro Senba (R) of Japan during a match in Tokyo on June 17, 2012
"With Ben Foden and James Wilson both out of action we're a bit light at full back, so Fa'atoina will add to our strength in depth in what is a crucial position," said Saints' director of rugby Jim Mallinder.
He added: "Fa'atoina has shown over the past 18 months that he has the ability to succeed at international level.
"So we are confident that he'll be able to fit in at Franklin's Gardens, especially alongside the Pisi brothers and Kahn Fotuali'i."
Autagavaia, who moves from Northland, has gained eight caps for Samoa over the past 18 months, including the recent autumn internationals against Ireland and Georgia.
The 25-year-old scored a first-minute try against Wales in November 2012 that set Samoa on the way to victory at the Millennium Stadium.