Despite the ability to determine feline blood types, the transfusion of canine blood to cats is still practiced in some countries. Xenotransfusion is effective—even if its effects only last for a few days—and is not associated with serious adverse effects. It avoids the need for blood typing, and most importantly, it avoids the transmission of intraspecific infectious agents, notably the feline leukemia virus (FeLV). Transfusion with canine blood is easier, quicker and less costly than transfusion with feline blood; it is less disagreeable for the donor. In the light of these arguments, when feline blood collected according to current guidelines is not available, in particular when the donor is not confirmed to be negative for the FeLV provirus, the authors consider it to be judicious to use canine blood for feline transfusion in emergency situations; this practice is preferable to inaction and to the inoculation of an infectious agent. Allotransfusion remains preferable in non-emergency situations as a treatment of chronic compensated anaemiae or if an appropriate donor (negative for FeLV provirus) is available. However, 2–4 days after a xenotransfusion, if a clinical alteration and a significant decrease in haematocrit are observed, a transfusion with cat’s blood confirmed to be negative for FeLV provirus should be performed. Xenotransfusion should never be used twice.