A　new　impedimetric　immunosensor　for　the　fast　determination　of　ochratoxin　A　(OTA)　in　food　samples　was　developed　based　on　the　instant　catalyst　as　enhancer.　Initially,　the　signal　tags　were　prepared　via　co-immobilization　of　anti-OTA　antibody　and　amine-terminated　dendrimer　(PAMAM)　on　the　graphene　oxide　nanosheets　through　the　covalent　interaction,　which　were　utilized　as　a　good　platform　for　combining　manganese　ion　(anti-OTA-GO-PAMAM-Mn2+).　Upon　target　OTA　introduction,　a　competitive-type　immunoreaction　was　implemented　between　the　analyte　and　the　immobilized　OTA-BSA　on　the　electrode　for　the　anti-OTA　antibody　on　the　graphene　oxide　nanosheets　labels.　After　a　competitive　immunoassay　format,　the　anti-OTA-GO-PAMAM-Mn2+　were　captured　onto　the　electrode　surface,　which　could　induce　the　in　situ　formation　of　MnO2　via　classical　redox　reaction　between　Mn2+　and　KMnO4　on　the　immunesensing　platform.　Moreover,　the　generated　MnO2　nanoparticles　act　as　efficient　catalyst　could　catalyze　the　4-chloro-1-naphthol　(4-CN)　oxidation　without　H2O2　to　generate　an　insoluble　precipitation　on　the　platform.　Under　the　optimal　conditions,　the　instant　catalyst　based　impedimetric　immunosensor　displayed　a　wide　dynamic　working　range　between　0.1 pg mL−1　and　30 ng mL−1.　The　detection　limit　(LOD)　of　the　assay　was　0.055 pg mL−1.　The　developed　method　exhibited　high　selectivity　and　can　be　used　for　the　determination　of　OTA　in　real　red　wine　samples.　©　2016　Elsevier　B.V.