Determination and quantification of small biomolecules is of immense importance in the world of biodiagnostic and health care industry. Among the different sensor technologies, organic electrochemical transistor (OECT) has shown tremendous potential owing to their low operating voltages and signal amplification. They have significant advantages such as miniaturization, feasibility, high throughput sensing and portability which given them an edge over other techniques. In the present study, an aptamer based OECT device has been developed to detect the presence of epinephrine. Epinephrine is a catecholamine which is responsible for flight or fight response of the body. The abnormalities in the level of Epinephrine is a direct indication of some disease such as pulmonary edema, Takotsubo cardiomyopathy, myocardial infarction and arrhythmias. The detection of epinephrine has been done using various techniques such as liquid chromatography, spectrophotometry, flow injection analysis, electrophoresis etc. All these methods are time consuming and require skilled labor and high-end instruments. As an alternative, aptamer based OECT device not only provides simple and compact approach but also provides a means for on-site testing in a timely and efficient manner. Upon addition of epinephrine in the OECT, the device showed a constant decrease in current which is observed in both transfer as well as current-time curve. The decrease was due to the oxidation of epinephrine in the vicinity of gate electrode which decreases the gate potential. A range of interfering species such as dopamine, ascorbic acid, DOPAC etc were also tested and no response was seen, which indicates high specificity of the approach. The present approach exhibited a detection limit of 90 pM with a response time in seconds which is by far the lowest detection limit achieved by any technique. The optimized aptamer based OECT sensor can be used to detect other biomolecules such as viral proteins, nucleotides, bacteria etc by designing the aptamer for the specific entity.