The Championship club revealed the Scotland international had passed a medical and would join on a three-year deal when his Inverness contract expires this summer.
Shinnie has been instrumental in Caley Thistle's success this season, scoring 15 goals from an advanced midfield role to put them on the verge of a Europa League place in third spot in the Clydesdale Bank Premier League.
His form earned him a Scotland cap in a 2-1 friendly victory over Luxembourg in November.
The 23-year-old also netted eight goals last season despite being out for several months with a broken foot.
Shinnie joined Caley Thistle from Rangers in 2011, having made just two substitute appearances for the Ibrox side.
Shinnie is the only confirmed departure from Terry Butcher's team this summer with top goalscorer Billy McKay among those tied up for next season, although midfielders Owain Tudur Jones and Aaron Doran have yet to sign.