A　new　electrochemical　immunosensing　protocol　was　designed　for　detection　of　carcinoembryonic　antigen　(CEA,　as　a　model　protein)　by　using　graphene-carried　poly(o-phenylenediamine)/gold　hybrid　nanosheets　(GNPGs)　as　signal　tags　on　the　hierarchical　dendritic　gold　microstructures　(HDGMs)-modified　glassy　carbon　electrode.　To　prepare　the　signal　tags,　poly(o-phenylenediamine)　molecules　were　initially　immobilized　on　the　surface　of　graphene　nanosheets　via　the　π-stacking　interaction.　Then　gold　nanoparticles　were　assembled　onto　the　poly(o-phenylenediamine)-modified　graphene　nanosheets,　which　were　used　for　the　labeling　of　anti-CEA　detection　antibodies　and　horseradish　peroxidase　(HRP).　The　as-prepared　GNPGs　were　characterized　by　using　atomic　force　microscopy　(AFM),　transmission　electron　microscopy　(TEM)　and　UV-vis　absorption　spectroscopy.　The　assay　was　carried　out　with　a　sandwich-type　immunoassay　format　in　pH　5.5acetic　acid-buffered　saline　solutions　containing　2.5mmolL-1　H2O2.　Under　optimal　conditions,　the　electrochemical　immunoassay　exhibited　a　wide　dynamic　range　of　0.005-80ngmL-1　toward　CEA　standards　with　a　low　detection　limit　of　5.0pgmL-1.　Intra-　and　inter-assay　coefficients　of　variation　were　less　than　11.5%.　No　significant　difference　at　the　0.05　significance　level　was　encountered　in　the　analysis　of　6clinical　serum　specimens　and　6spiked　blank　new　born　cattle　serum　specimens　between　the　developed　immunoassay　and　commercially　available　electrochemiluminescent　(ECL)　method　for　the　detection　ofCEA.　©　2013　Elsevier　B.V.