Stone was offered a new contract at the County Ground, but has instead opted to move to Edgbaston for the start of next season.
The news came as a real disappointment to Northants, who have nurtured the 22-year-old and are currently helping him with his rehabilitation from a serious knee injury.
Academy graduate Stone took to social networking site Twitter to stress that he is grateful for the support he has received throughout the past nine years.
He wrote: “Just wanted to thank everyone at Northants who have helped me to progress over the past nine years.
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“I wouldn’t have got to where I am without the coaching, off-field and playing staff at the club.
“I have been lucky enough to play in finals, win trophies and get promoted, these are things I will never forget!
“I am obviously excited by the prospect of moving to Warwickshire CCC.
“I’m grateful to them for giving me an opportunity to continue my progression and hopefully push for honours both in county and international cricket.
“I will always keep Northants close to my heart and am looking forward to supporting them in the upcoming quarter-finals.”