Baptiste, who can play at full-back or in central defence, makes the short switch from the Macron Stadium to Ewood Park on a season-long deal.
The 28-year-old began his career with Mansfield where he made almost 200 appearances in a six-year spell with the Stags.
A move to Lancashire followed, signing for Blackpool in the summer of 2008, and he was a key member of Ian Holloway's side as the Tangerines clinched promotion to the Premier League via the play-off final at Wembley in 2010.
After 190 appearances for the Seasiders, Baptiste joined Bolton last summer.
He made 43 appearances in all competitions for Wanderers during the 2013/14 campaign and scored four goals, including the consolation in a 4-1 defeat at Ewood Park last August.