The 31-year-old batsman, who has previously played for Warwickshire, Durham and most recently, Derbyshire in England, comes into the Sharks squad to replace Phil Salt, who has now joined England’s ODI group.
MacLeod has played 49 IT20s and 66 ODIs for Scotland, and scored an unforgettable century in his country’s famous win against England in 2018.
“I’m absolutely delighted to be down here in Sussex,” said MacLeod. “It’s an exciting opportunity to get out there and play some cricket.
“I’ve got some good experience having played in the Blast before and hopefully I can add some experience to the dressing room to help win a few games.
“It’s a very exciting white-ball squad. Sussex are always a team that when they’re on Sky, I sit down and watch them. They’ve always been a team I’ve looked at to see how they do things.
“Matt Machan and Stu Whittingham, when we were away with Scotland, always spoke so well of the club, so to get the opportunity to come here and play, and see what this T20 team can do, is one that I’m thoroughly looking forward to.”
Sussex head coach, Jason Gillespie added: “Calum is an experienced cricketer, and a good T20 player.
“He’s performed well in the Blast in the past and we believe he will be a good addition.
“We’re missing a couple of players, and with Salty joining the England squad, it’s good to have another option at the top of the order.”
Since making his international debut in 2008 against England, MacLeod has scored 2,175 ODI runs and 1,042 IT20 runs.
His highest ODI score of 175 came against Canada, and he starred against England in Edinburgh two summers ago, when Scotland secured their first ever win against their rivals in dramatic fashion.
MacLeod’s unbeaten 140 came off 94 balls with 16 fours and three sixes to help his side win a thrilling match against the world’s top-ranked side by six runs.
In IT20s, MacLeod’s best score of 72 came against Ireland in 2019, while he has also played franchise cricket in Canada’s Global T20 tournament and the Afghanistan Premier League, and in 2018, scored a century in the Vitality Blast for Derbyshire Falcons.
The experienced batsman goes straight into the Sharks squad for Thursday night’s match against Hampshire at The Ageas Bowl.