The New Zealand star was unveiled as an overseas signing on Monday morning, with the County confirming the 31-year-old will be with the club for the duration of the tournament, that starts at the end of May.
The all-rounder has previously played in the Blast for Derbyshire Flacons, Kent Spitfires and Essex Eagles, and was a Welsh Fire team-mate of Steelbacks skipper Josh Cobb in The Hundred last summer.
“I’m excited to get going with Northamptonshire in 2022.” said Neesham, who was a part of the New Zealand team that reached the final of the ICC T20 World Cup in November.
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“The club has a fantastic history in the Blast and I hope that we can recreate those successes from 2013 and 2016.”
Neesham is a proven world-class white-ball performer.
As well as helping his country to the T20 World Cup final last year, he was also in the Black Caps team that was edged out by the narrowest of margins in the 2019 50-over World Cup Final at Lord's.
Indeed, it was Neesham who hit 13 from five balls in the Super Over to take his country to the brink of glory, only to be stranded at the non-striker's end and see Martin Guptill run out going for what would have been the winning run.
The all-rounder has close to 2,400 runs and 158 wickets to his name in T20 cricket, boasting a strike rate of 136 with the bat - that rises to more than 150 in T20 internationals.
Steelbacks skipper Cobb is delighted to have captured the signing of Neesham, having seen him at close quarters in The Hundred last summer.
“Having spent time with Jimmy at the Welsh Fire last year I know what he can bring to us,” said Cobb.
“He’s a three dimensional cricketer with genuine power and a high strike rate in the middle order, but it was his character that stood out to me.
"He’s someone who wants to win and is very selfless, he’s a real team first kind of player.
“I’m looking forward to having him here as a leader, to pass on his experience and help drive us to be better.”
Neesham will join the Steelbacks for the entirety of the 2022 Blast North Group campaign as well as any knockout matches, and will also be available for selection for the home LV= Insurance County Championship Division One fixture against Warwickshire in June.
That was also an attraction to Neesham, who has also won 12 Test caps for his country.
“The opportunity to possibly play some first-class cricket for the county in division one is also an exciting challenge,” said Neesham.
“I look forward to linking up with everyone at Wantage Road soon."