A fluid mixing and distribution device for a catalytic downflow reactor, said device comprising a collection zone (A), a mixing zone (B) comprising a mixing chamber (15) for fluids and an exchange chamber (16) for fluids, a distribution zone (C), said exchange chamber (16) comprising at least one upper lateral cross-section of flow (17a) and at least one lower lateral cross-section of flow (17b) through which fluids can pass from said exchange chamber (16) to said distribution zone (C), characterized in that said exchange chamber (16) comprises a fluid deflection means (24) fixed to said exchange chamber (16) and located downstream of the upper lateral cross-section of flow (17a), said fluid deflection means (24) forming with said exchange chamber (16) a space (26) in the shape of a pan.