Shackell, 31, has signed a three-year deal at the iPro Stadium after he was granted permission to speak to the East Midlands side on Thursday afternoon.
He made 49 appearances for the Rams in the 2011/12 season and rejoins after making 136 appearances for the Clarets.
Speaking of the deal earlier today, Clarets boss Sean Dyche said:
“Jason really made it clear to me last year, and it's fair to say Derby County made an offer that was so large he found he couldn't refuse it.
“Outside the Premier League there are still some clubs throwing enormous amounts of money at the situation, and Derby are one of those clubs.
“His motivation was to go there for the contract that was on offer."