Platelet transfusion, also known as platelet concentrate, is used to prevent or treat bleeding in people with either a low platelet count or poor platelet function. Often this occurs in people receiving cancer chemotherapy. Preventive transfusion is often done in those with platelet levels of less than 10 x 10⁹/L. In those who are bleeding transfusion is usually carried out at less than 50 x 10⁹/L. Blood group matching (ABO, RhD) is typically recommended before platelets are given. Unmatched platelets, however, are often used due to the unavailability of matched platelets. They are given by injection into a vein.

Side effects can include allergic reactions such as anaphylaxis, infection, and lung injury. Bacterial infections are relatively more common with platelets as they are stored at warmer temperatures. Platelets can be produced either from whole blood or by apheresis. They keep for up to five to seven days.

Platelet transfusions came into medical use in the 1950s and 1960s. It is on the World Health Organization's List of Essential Medicines. Some versions of platelets have had the white blood cells partially removed or been gamma irradiated which have specific benefits for certain populations.