Samoa in Tietjens coup
Samoa in Tietjens coupSHARE
This comes just a month after Tietjens quit his New Zealand job, following the side's failure at the Rio Olympics.
Samoa Rugby Union Chairman Tuilaepa Sailele Malielegaoi, who is also the Pacific nation's Prime Minister, described Tietjens' appointment as "a great coup for Samoan rugby".
"We know that there was much competition to secure the services of such a prestigious figure," he said.
Rising Sevens power Kenya were believed to have been close to signing Tietjens, who guided New Zealand to 12 Sevens World Series titles, four Commonwealth gold medals and two Sevens World Cup crowns.
Tietjens, a World Rugby hall of famer, said he was excited about coaching a nation that was passionate about Sevens and had an abundance of natural talent.
Samoa did not qualify for Rio and Tietjens said he wanted to get them to the 2020 Olympics in Tokyo.
"My goal as a coach is to get Samoa to where they need to be and that's at the top of the tree in Sevens rugby," he told reporters.
The 60-year-old said when he resigned last month that he would not assist any of New Zealand's rivals.
He was undaunted at dealing with the notorious politics and in-fighting that have plagued Samoan rugby in recent years, including the sacking of his predecessor Damian McGrath last month.
In apparent reference to McGrath's dismissal less than a year into his contract, Tietjens warned that it would take time to turn around Samoa's fortunes.
"It's actually quite exciting to have someone that leads your country involved in Samoan rugby, it's never happened to me in the past in New Zealand," he said.
"All we're wanting is Samoan [success], but I assure you it's not a quick fix.
"It's going to take a gradual amount of time to select the players that you need and [complete] talent identification."
More than 40 All Blacks graduated through Tietjens' notoriously gruelling Sevens programme, including greats such as Jonah Lomu and Christian Cullen.
However, the New Zealanders were eclipsed in recent years by Fiji and finished a disappointing fifth in Rio.