The 26-year-old centre, who can also play at second row, has penned a deal with the Super League club until the end of next season.
Sa was part of the New Zealand squad that won the rugby league World Cup in 2008.
"Setaimata is a great signing for us," Hull coach Lee Radford is quoted as saying by Sky Sports News. "He is exactly the calibre of player we should be bringing into this club and a significant move in terms of our recruitment process."
Sa's move to Hull sees him return to rugby league following a two-year spell with Catalans Dragons from 2010 to 2012.