Needle support assembly for a venous blood collection device with evacuated vial, comprising a support body having a coupling seat for a vein needle and coupling seat for a vial needle. The support body is provided with an inner chamber having an entrance and an exit. The support body is made at least partially in transparent or semi-transparent material to permit the visualization of the blood flow. The inner chamber has a mean cross-section greater than the cross-sections of both the coupling seats and is divided into compartments communicating with each other which define one or more channels for the blood flow from the entrance to the exit. Each channel defines a path for the blood which moves away from the entrance to the exit. Each channel defines a path for the blood which moves away from the straight line connecting the entrance and the exit and has a smaller cross-section than the mean cross-section of the inner chamber.