Improvement of imaging methods has led to more incidental adrenal tumor findings, especially adenomas. Routine hormonal evaluation uses only a few steroids to evaluate possible hormonal hypersecretion of these adenomas, but a wide spectrum of serum steroid hormone changes has not been published. To measure the serum levels of 83 steroids from patients with unilateral and bilateral adrenal incidentalomas to uncover full steroid profile changes in patients with subclinical hypercortisolism (SH). Cross-sectional study. The study was conducted at a tertiary inpatient clinic. Fifty-two patients with adrenal incidentalomas (unilateral, n = 29; bilateral, n = 23), including nonfunctioning (n = 11) vs SH (n = 41), and 26 age- and sex-matched controls from the general population were included. Eighty-three serum steroids were measured by gas chromatography-tandem mass spectrometry (GC-MS/MS) before and after 1 mg dexamethasone, ACTH, midnight serum cortisol, and urinary free cortisol/24 hour. Of 83 measured steroids, 10 were significantly decreased in patients with SH, including dehydroepiandrosterone sulfate (DHEAS), androsterone sulfate, epiandrosterone sulfate, androstenediol sulfate, conjugated 5α-androstane-3β,17β-diol, and conjugated 5α-androstane-3α,17β-diol. This finding was observed even when unilateral, bilateral, male, and female subgroups were analyzed separately. When we compared routine clinical methods and GC-MS/MS‒measured steroids, the most discriminatory was DHEAS followed by midnight serum cortisol, epiandrosterone sulfate, androsterone sulfate, ACTH, and 16α-hydroxypregnenolone. SH was associated with decreased levels of adrenal androgens, their metabolites, and pregnenolone metabolite. GC-MS/MS is a powerful tool for measuring serum levels of these undescribed changes in steroid metabolism, which are characteristic of SH in adrenal incidentalomas.