Redfern, who made his debut for the county as a 16-year-old in 2006, was handed an improved deal in October 2012 but leaves the club by mutual agreement after a disappointing season.
Derbyshire head coach Karl Krikken said: "Dan's been with the club since joining the academy in 2004 and we thank him for his efforts during that period.
"However, in recent times, he's had a number of issues - both on and off the field - which made last season in particular a challenging time for both him and the club.
"While it's always difficult to see players leave, both Dan and the club feel a new challenge is the best route forward."
Redfern made two centuries in 70 first-class matches for Derbyshire and said: "The decision to move on is tough but a fresh start will open new opportunities for me in the next stage of my career."
- Sports & Recreation
- Karl Krikken