OBJECTIVES: Testosterone and cortisol are the end products of the hypothalamus-pituitary-gonadal and hypothalamus-pituitary-adrenal axes. Both hormones affect brain anatomy and brain activity, which is positively correlated with the testosterone/cortisol ratio. The aim of the present study was to observe the main effect and interaction between testosterone and cortisol in relation to brain activity and whether it is possible to predict neuroendocrine levels. METHODS: Sixty-seven participants were included for evaluating saliva hormones and resting state EEG. The levels of cortisol and testosterone were measured by enzyme-linked immunosorbent assay. The free artifacts of the EEG signals was computed and compared with the normative database. RESULTS: The results showed that the testosterone/cortisol ratio was 34.21±3.75 in males, 19.92±1.47 in females and 24.19±1.71 among all participants. The testosterone/cortisol ratio and the resting state EEG delta/beta ratio were correlated at the frontal area, the central area, the parietal area and the left temporal area but not at the right temporal area or the occipital area. The resting state EEG delta/beta ratios of the frontal and central areas were used in a multiple regression model to predict the testosterone/cortisol ratio as 32.0% in males, 11.9% in females and 14.3% among all participants. CONCLUSION: Resting state EEG is a non-invasive approach that can be used to estimate hormone levels, which are possible biomarkers of physiological and psychological disorders.