Glycoprotein (GP)-specific platelet antibodies can cause allo-immune and auto-immune thrombocytopenia. The specific detection of relevant antibodies is a prerequisite for diagnosis and treatment. Here, we describe an improved method based on simultaneous detection of various platelet-specific immunoglobulin G (IgG) and IgM antibodies. Bead populations with distinct fluorescence intensities, coated with monoclonal antibodies specific for mouse heavy chain isotypes, were used for the simultaneous immobilization of platelet-GP [IIb/IIIa, Ib/IX, human leucocyte antigen (HLA) class I, or Ia/IIa, CD32, GPIV or CD109, Ib/IX, HLA class I]. In order to detect human IgG and IgM antibodies simultaneously, phycoerythrin- and fluorescein isotiocyanate-conjugated goat anti-human IgG and IgM were added. On this basis, the abundance of six distinct antibodies (three anti-GP, each with subclasses IgG and IgM) were simultaneously analysed without cross-reaction by flow cytometry. For evaluation, sera and platelets from 169 patients with platelet-binding and/or platelet-associated antibodies were investigated. The monoclonal antibody-specific immobilization of platelet antigen (MAIPA) assay was performed in parallel as reference test. The simultaneous analysis of platelet-specific antibodies (SASPA) assay was able to detect all platelet-specific IgG and IgM that were also recognized by MAIPA with a comparable sensitivity. SASPA proved to be a rapid and reliable assay that required less platelets than other methods. This method has the potential to pave the way for new investigations of platelet-specific antibodies.