Florian Jozefzoon has decided to join Derby County and reject a move to Leeds United, according to Sky sources.
The 27-year-old Dutch winger has already completed a medical with the Derbyshire club ahead of joining on a three-year deal.
Sky Sports News reported earlier on Thursday that Leeds had matched the Rams' £2.75m bid - both of which were accepted by Brentford.
Derby had an initial £1.5m bid knocked back by the Bees earlier in the window.
Jozefzoon, who scored seven goals in 43 appearances last season, moved to Griffin Park from PSV Eindhoven in January 2017 and has just a year left on his current contract.
Brentford have already signed a replacement in Said Benrahma from Nice, with the Algeria attacker agreeing a four-year contract with a year's option on July 6.