His signing will not prove universally popular throughout the English game. "It's one of those where you probably prefer them not to get any game time in England before the Ashes," Test captain, Ben Stokes, said when asked about the prospect during the tour of Pakistan. "It is what it is."
Smith will be available for Sussex's trips to Worcestershire, starting on May 4, and Leicestershire, as well as the home fixture against Glamorgan, starting on May 18 - a game which will likely pit him against Australia team-mate Marnus Labuschagne.
"I am excited about joining Sussex for a few games in May and hopefully making a contribution to a successful season," Smith said. "I am particularly looking forward to working with the younger players in the squad and hoping I can provide some guidance to them."
Smith, who had a short T20 spell with Worcestershire in 2010, will join Cheteshwar Pujara as one of Sussex's overseas signings, with the club also working to bring in a bowler after Jayden Seales was ruled out of an early season stint by injury.
Sussex Cricket CEO, Rob Andrew, said: "We are thrilled to have Steve Smith available for our County Championship matches in May. To have arguably the world's best batter play for Sussex just before an eagerly awaited Ashes Test series is great for us and the County Championship.
"Our Championship form has not been good enough for a number of years, and under the new direction of head coach Paul Farbrace, we are looking to be positive and ambitious.
"Being able to attract a player of Steve Smith's calibre is a massive statement and will be of great benefit to our young homegrown players, particularly our crop of talented young batters."