Opening batsman Ben Slater will join Nottinghamshire at the end of the season on a three-year deal.
He will initially move to Trent Bridge on a loan deal for the rest of the 2018 campaign, subject to final approvals.
The Chesterfield-born batsman was offered an improved deal at Derbyshire, but has made the decision to leave the club after 14 years with the county.
The 26-year-old, who progressed from the county age groups and into the first team, made his debut in 2013 and went on to feature in 92 matches across all formats, scoring 4,641 runs.
Chief executive Simon Storey said: “We have been talking to Ben’s representative for some time now and we put significantly improved terms on the table. Ben and his agent have acted professionally throughout the negotiations which have remained confidential.
“As a product of our Cricket Derbyshire pathway, Ben has become an accomplished opening batsman, especially in 50-over and red-ball cricket. Whilst we are disappointed that Ben has chosen to pursue his career elsewhere, we all wish him well.
“The new head of cricket will be supported to ensure that Ben’s contributions with the bat at the top of the order can be replaced.”
Slater added: “This has been an extremely difficult decision and not one I have taken lightly. I have loved playing for my home county and would like to thank the Derbyshire members, all of my teammates and the club as a whole.
“The club made me a great offer to stay, but this has come down to a cricketing decision.
“I now have the opportunity to test myself, play at a Test match venue and work with a highly-regarded coaching team who have identified a role for me in their squad.
“I know the new set-up that Derbyshire are now pursuing with a head of cricket and additional coaching support will help the club make further progress going forward.
“The dressing room is a great place to be and the quality of the youngsters coming through shows the intent and commitment Derbyshire has in developing its own. I wish them every success for the future.”