Competitive electrochemical immunosensor for the detection of histamine based on graphene modified electrode and horseradish peroxidase (HRP) initiated deposition of insulating film was developed. After the immobilization of anti-histamine antibodies onto graphene surface, free histamine and HRP tagged histamine molecules will compete to bind with the antibodies. The captured HRP could then catalyze the polymerization of 3,3'-dimethoxybenzidine (DB) in the presence of H2O2 to produce the deposition of an insulating polymer film, poly(3,3 '-dimethoxybenzidine) (PDB) onto electrode surface. The deposited insulating PDB film resulted in the decrease of the electrochemical current of the electrode in Fe(CN)(6)(3-/4-) solution, and the current change is proportional to the concentration of histamine detected. The proposed immunosensor displays wide linear range towards histamine detection (1 pg/mL-1 ng/mL) with a detection limit of 0.5 pg/mL. The immunosensor was applied to the detection of histamine in serum samples with satisfactory results. (C) 2014 Elsevier B.V. All rights reserved.