A multiple blood sampling device includes a housing having a chamber therein, a first cannula attached to one end of the housing, a second cannula attached to the other end of the housing, and a one-way valve provided within the housing. Part of the housing is molded around a portion of the valve to securely hold it in place. Another portion of the valve extends into the chamber where it provides valving action in response to the relative pressures in to two cannulas. When one cannula penetrates the blood vessel of a patient and the other punctures the stopper of an evacuated tube, blood is able to flow through the device and into the tube. Backflow is prevented by the one-way valve.