The 34-year-old Samoan forward who spent five years at The Rec is to play rugby legend Jonah Lomu in a film about the 1995 Rugby World Cup.
New Zealand-born Feaunati, who retired last season, will appear alongside Morgan Freeman and Matt Damon.
Feaunati, now the director of rugby at a school in the Midlands, plays Jonah Lomu in The Human Factor, which centres on the relationship between then South African president Nelson Mandela and that nation's captain François Pienaar.
Freeman plays Mandela in the movie, for which Feaunati was chosen following a screen test in London after being recommended by Bath prop David Barnes, who is also chairman of the Professional Rugby Players' Association.
The test saw him demonstrate the famous haka ritual which has become the hallmark of the All Blacks ahead of international rugby games.
Feaunati told the BBC: "I had to talk about myself for the casting director, and then she asked me to do the haka.
"I might have scared one or two of the ladies, but I guess it did the trick."
The competition was staged in South Africa in 1995 and was won by the host nation.
Feaunati, who won 13 international caps for Samoa, added: "The first call I got about it was from my old team-mate David Barnes, asking me if I wanted to be in a Clint Eastwood film, so I was 99 per cent sure it was a prank.
"But when I got a further call from the PRPA offices, it dawned on me that maybe this was serious."
He made 131 appearances for Bath between 2003 and last summer."