Biomarkers are biological parameters that can serve as a means for detection, risk assessment, prognosis and monitoring of homeostasis or pathologies. Cortisol is the stress hormone and is found in its purest form in saliva. Even though it is very important for regular physiological functions, such as controlling blood sugar levels and reducing hypertension, its imbalance can cause several problems, being related to psychological stress and Parkinson’s disease, for example. The objective of this work is to provide a quick and effective way to detect salivary cortisol, making it react with the Salkowski reagent and then using spectrophotometry for its analysis. A circuit was developed to build the portable spectrophotometer, using a 420nm LED and a sensor that is sensitive to the same range. Furthermore, the device was integrated with an application, for greater dynamic information. The expected result of the project is to achieve a quick and efficient way to detect cortisol, in this way, patients who could suffer neurological disorders due to the amount of the biomarker, previously detected the problem for treatment. As a future project, the aim is to carry out tests with groups of individuals to validate the effectiveness and precision of the equipment developed, and then work on the prototype in order to turn it into a product.