The 21-year-old was a rare bright spark for West Ham last season, joining from Slavia Prague in July and going on to make 34 appearances, providing five assists in the process.
Diouf was ultimately powerless as West Ham were relegated one the final day of 2025-26 but now looks set to return to the Premier League.
According to BBC Sport, the Hammers have accepted a massive £40 million bid from Keith Andrews’ impressive Brentford.
It’s understood the deal consists of an initial £35m, with a further £5m in add-ons, with Diouf now set to undergo his medical.
The Senegal international had been Brentford’s priority defensive target this summer but talks had stalled before being reopened this week.
Diouf could now become their fifth signing of the transfer window, following in the footsteps of Callum Wilson, midfielder Mamadou Sangare, centre-back Jannik Schuster and winger Jaidon Anthony.