The 60-year-old coached the All Blacks Sevens from 1994 until September, stepping down
after an unsuccessful Olympic campaign in which his side suffered a shock loss to Japan in the pool stage before losing to eventual champion Fiji
in the quarterfinals.
"We know that there was much competition to secure the services of such a prestigious figure in world rugby sevens," Samoa Rugby Union chairman Tuilaepa Sailele L. Malielegaoi said in a statemen
t posted on the official Manu Samoa Facebook page.
"In entrusting our beloved sevens team to Gordon, we know we have a coach who understands how important rugby is to our people, and he has a deep appreciation for how to get the best out of the talent we know we have."
Tietjens was inducted into the International Rugby Board's Hall of Fame in 2012.
He is the most successful sevens coach in history having won 12 Sevens World Series titles, two World Cup titles, and four Commonwealth golds.
Tiejtens is also credited for bringing through many players who then went on to star for the All Blacks 15-a-side team, including Jonah Lomu, Joe Rokocoko and Sonny Bill Williams.
Samoa failed to qualify for the Rio Olympics, the first time the sport's shortened format was played at the Games, after suffering a shock defeat to Spain.
The nation does, however, have a history of performing strongly in rugby sevens. It won the 2009-10 World Series from Tietjens' second-placed New Zealand team and was third overall in 2006-07 and 2007-08.
The 2016-17 Sevens World Series begins in Dubai in early December, while Tietjens will take up his role with Samoa in the new year.
He replaces Damian McGrath, now coach of Canada's sevens team after being sacked last month
. The Englishman led Samoa to the Paris Sevens title in May
and ninth overall in the series, four places above Canada.
"I have some commitments I need to complete before making the transition to Samoa, but I am hugely excited to be joining the 'Boys in Blue,'" Tietjens said.
"I am massively motivated to help them achieve their goal to be a consistent top performer on the world stage."