A　new　sandwich-type　impedimetric　immunosensor　based　on　functionalized　graphene　oxide　nanosheets　with　a　high　ratio　of　horseradish　peroxidase　(HRP)　and　detection　antibody　was　developed　for　the　detection　of　carcinoembryonic　antigen　(CEA)　by　coupling　with　enzymatic　biocatalytic　precipitation　of　4-chloro-1-naphthol　(4-CN)　on　the　captured　antibody-modified　glassy　carbon　electrode.　Two　molecular　tags　(with　and　without　the　graphene　oxide　nanosheets)　were　investigated　for　the　detection　of　CEA　and　improved　analytical　features　were　acquired　with　the　graphene-based　labeling.　With　the　labeling　method,　the　performance　and　factors　influencing　the　properties　of　the　impedimetric　immunosensors　were　also　studied　and　evaluated.　Under　the　optimal　conditions,　the　dynamic　concentration　range　of　the　impedimetric　immunosensors　spanned　from　1.0　pg　mL(-1)　to　80　ng　mL(-1)　CEA　with　a　detection　limit　(LOD)　of　0.64　pg　mL(-1).　Intra-　and　inter-assay　coefficients　of　variation　were　less　than　7.5%　and　11%,　respectively.　Additionally,　the　methodology　was　evaluated　for　CEA　analysis　of　10　clinical　serum　samples　and　5　diluted　serum　samples,　receiving　in　a　good　accordance　with　the　results　obtained　by　the　impedimetric　immunoassay　and　the　commercialized　electrochemiluminescent　method.　(C)　2013　Elsevier　B.V.　All　rights　reserved.