The 25 year old could end up costing Rovers £3million, but he arrives on a four year deal and will be a major boost to the squad.
have agreed a fee of more than £3million for the 25-year-old, who has penned a four-year contract at Ewood Park.
The club confirmed the switch in a statement on their website, which read: "Blackburn Rovers have this evening completed the signing of Leon Best from Newcastle United.
"The 25-year-old striker makes the move from the North East to the North West for a fee of more than £3m, signing a four-year deal."
Nottingham-born Best began his professional career at Southampton and during three years on the south coast spent time out on loan at QPR, Sheffield Wednesday, Bournemouth and Yeovil.
In 2007 he joined Coventry, where he spent three years before being signed by Newcastle for £1.2million in February 2010.