Vincent last played first-class cricket in 2008
Sussex have signed New Zealand batsman Lou Vincent, Pakistani left-arm seamer Naved Arif and South African all-rounder Kirk Wernars.
Vincent, 32, who has played 23 Test matches, will soon obtain a British passport and is expected to be available from May.
Arif, 29, qualifies to play county cricket through his Danish wife, while Wernars, 19, has a Dutch passport.
All three men have agreed one-year deals at Hove.
Vincent, who has previously had spells with Lancashire, Northants and Worcestershire, has also played 102 one-day internationals.
The Kiwi has agreed a deal to play one-day cricket, but will also provide cover in the County Championship.
Lou (Vincent) is an experienced international batsman who can turn a game in his own right - and he's a brilliant fielder
Sussex professional cricket manager Mark Robinson
Arif has previously played for Pakistan A, while Wernars has represented South Africa at under-19 level.
"Our priority all winter has been to strengthen the bowling and ideally bring in an all-rounder as well. To do that and to be able to bring a proven match winner like Lou is exciting and sets us up nicely for the summer," said Sussex professional cricket manager Mark Robinson.
"Naved is a late developer, and with his background in Pakistan he's had to do it the tough way. His record out there on unhelpful wickets is outstanding and he's got the potential to change games.
"We've had many good reports about Kirk over the winter through our South African connections, he's a lad with promise and a genuine all-rounder. He hits the ball hard and can open the bowling as well, which will give us more options.
"Lou is of course an experienced international batsman who can turn a game in his own right, and he's a brilliant fielder. He's on an initial one-day contract but will cover the four-day team when needed."
Sussex are also looking to make a further overseas signing to play in the Friends Provident t20.