The all-rounder joins New Zealand internationals Colin de Grandhomme and Jeetan Patel at the Birmingham Bears after signing a Kolpak deal, which means he gives up his right to play for his country and is not classed as an overseas player in county cricket.
The South Africa-born 38-year-old confirmed his retirement from the Black Caps after an awards night on Thursday.
"Loved playing with the @BLACKCAPS and to have made some special friendships along the way. A team environment I will never forget," he wrote on Twitter, posting a picture of himself with New Zealand fast bowler Tim Southee and captain Kane Williamson.
Elliott played 83 one-day internationals and five test matches, with his last New Zealand match in the semi-finals of the World Twenty20 against England a year ago.
A destructive batsman when on song and a handy swing bowler, Elliott will be remembered in New Zealand for his starring role for the co-hosts at the World Cup.
He scored an unbeaten 84 in the Auckland semi-final, with his six on the second-last ball sending a packed Eden Park into raptures, while leaving a number of South Africa players in tears.
He then top-scored for the Black Caps with 83 in their loss to Australia in the final.
(Reporting by Ian Ransom; Editing by Peter Rutherford)
