A bifurcated venous return cannula assembly is described for insertion into the vena cavae through a single incision in the right atrium. The cannula includes a single outward tube that is bifurcated at an inward end, forming two normally diverging flexible branches. The tube branches diverge naturally from the central axis of the single tube. An obturator slidably engages the bifurcated end of the tube to hold the branches together along the tube axis during initial insertion and to draw the branches back together within the atrium upon withdrawal. The obturator also enables the branch ends to separate within the atrium following initial insertion. The separating tube ends seek out and ascend the superior vena cava, and descend the inferior vena cava due to the natural resiliency of the branches and their tendency to seek their normal diverging positions.