The striker has agreed to join Steve Kean's recently relegated side for £3 million after failing to fully establish himself in Alan Pardew's first team last season
The Ewood Park outfit have confirmed the capture of the Republic of Ireland international, who will wear the number nine shirt after ending his two-year spell on Tyneside.
The 25-year-old struggled to secure a place in Alan Pardew's starting line-up last season following the January arrival of Papiss Cisse, who made an impressive start - scoring 13 goals in 14 appearances.
Best's scored 10 goals in 42 appearances for the Magpies after joining from Coventry City in 2010 and earnt his first full international honours with the Republic of Ireland.
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However, an injury to his knee which kept him out of the final three months of the season ended his chances of making Giovanni Trapattoni’s squad for Euro 2012.
Best becomes the second signing of the summer for the recently relegated Lancashire outfit, after Danny Murphy joined the club following the expiry of his contract with Fulham.