The 24-year-old Scotland international follows the arrivals at Pride Park of goalkeeper Frank Fielding and strikers Jamie Ward and Theo Robinson.
May the fourth be with you: Derby have made Kilmarnock skipper Craig Bryson (L) signing No 4 of the summer
Derby boss Nigel Clough said: 'It's a tremendous signing for us and we're delighted that Craig has chosen to come to Derby.
'He's a leader on and off the field and has a tremendous hunger to improve.
'We've watched him in action repeatedly over the last six months and he has energy and ability in abundance.
Changing times: Derby boss Nigel Clough is continuing his rebuilding job at Pride Park after a disappointing finish last season
'At age 24 he's a player we see having a big impact both now and in the future.'
Bryson, who started 33 of Kilmarnock's 38 Scottish Premier League games last season, skippered the side to a sixth-placed finish.
He made his full international debut in November last year against the Faroe Islands.
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Explore more:People: Theo Robinson, Nigel Clough, Jamie Ward Places: Scotland Organisations: Scottish Premier League