The 18-year-old winger finalised his contract at the club's offices in Sant Joan Despí on Friday in a deal worth around €8.5m, putting pen to paper on a five-year deal that runs until 2031. He joins Anthony Gordon and Karim Adeyemi as Barcelona's third attacking recruit of the window, with Flick continuing to prioritise pace and directness out wide.
Bisiwu travelled straight to England after signing to join Barcelona's pre-season camp at St George's Park, where Flick's squad face Birmingham City and will remain until Monday.
The head coach wants to assess the Belgian up close before deciding whether he follows the path of Roony Bardghji last year and gets a look-in with the first team, or begins the campaign with Barça Atlètic in Segunda RFEF, likely to be the more probable route given the numbers already ahead of him out wide.
Primarily a left winger capable of playing off the right as well, Bisiwu is regarded internally as a long-term project rather than an immediate contributor. Club Brugge retain a sell-on percentage as part of the deal, a fairly standard clause when selling one of their academy graduates.
Born in January 2008 to a family of Ghanaian descent, Bisiwu began his career at Leuven before moving to Brugge's academy, where he progressed to Club NXT — Brugge's reserve side, playing in Belgium's second tier — accumulating 36 appearances there.
He also impressed for Brugge's youth side in the UEFA Youth League over each of the past two seasons, scoring three goals in 14 appearances, and was part of the Belgium squad that made the team of the tournament at last year's European Under-17 Championship.
Should he break through, Bisiwu would become just the third Belgian to represent Barcelona's first team, following Thomas Vermaelen and Patrick Goyvaerts.
For now, sporting director Deco and the club's recruitment staff view him as exactly the kind of long-term investment Barcelona have increasingly targeted in recent transfer windows: promising, inexpensive relative to his ceiling, and signed before his price becomes prohibitive.