The knowledge of pseudothrombocytopenia (PTCP) is important for the accuracy of a clinical assessment and for avoiding unnecessary treatment. An elderly patient was hospitalized with left lung pneumonia. Severe thrombocytopenia [platelet (PLT) number: 18 × 109/L] without any clinical bleeding was found in ethylenediaminetetraacetic acid blood collection tube. PLT measurement was repeated in various anticoagulant [sodium citrate, lithium heparin, disodium oxalate, hirudin, and magnesium sulfate (Mg-sulfate)] sample collection tubes and all of them showed thrombocytopenia except with Mg-sulfate. To the best of our knowledge, PTCP with five anticoagulant sample collection tubes has not been reported earlier.