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　pi-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　5.5　acetic　acid-buffered　saline　solutions　containing　2.5　mmol　L-1　H2O2.　Under　optimal　conditions,　the　electrochemical　immunoassay　exhibited　a　wide　dynamic　range　of　0.005-80　ng　mL(-1)　toward　CEA　standards　with　a　low　detection　limit　of　5.0　pg　mL(-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　6　clinical　serum　specimens　and　6　spiked　blank　new　born　cattle　serum　specimens　between　the　developed　immunoassay　and　commercially　available　electrochemiluminescent　(ECL)　method　for　the　detection　of　CEA.　(C)　2013　Elsevier　B.V.　All　rights　reserved.