Tyramine is a naturally occurring monoamine compound produced from decarboxylation of the amino acid tyrosine by monoamine oxidase. Foodstuffs containing considerable amounts of tyramine include fish, fermented food, and other dairy products. High levels of tyramine in food samples cause toxic effects such as migraine, tachycardia, and vomiting. Therefore, sensitive methods are required to monitor and detect tyramine. Here, a competitive colorimetric immunosensor was developed for ultrasensitive detection of tyramine in fish samples. Tyramine-bovine serum albumin was coated on a microplate and introduced as an analyze competitor. Competitive assays were achieved by incubating free tyramine and horseradish peroxidase (HRP)–labeled monoclonal anti-tyramine antibodies. After the competitive reaction, captured HRP catalyzed the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H₂O₂) to produce color responses. The competitive colorimetric immunosensor showed good performance with low detection limit (2 ng/mL), wide linear range (from 5 to 40 ng/mL), high precision (% RSD = 3), and good selectivity in tyramine detection. Applicability of the proposed immunosensor was evaluated by analyzing tyramine in fish samples. Detection of tyramine in real samples showed good recovery and corroboration with the HPLC method. Results indicated that this method can be successfully used for analysis and safety control of tyramine in food samples.