The diagnostic work-up of adrenal tumors, often incidentally discovered, has emerged as an ever-increasing diagnostic problem for clinical endocrinologists. No imaging modality has sufficiently high sensitivity and specificity at differentiating benign from malignant adrenal lesions. It has long been observed that adrenocortical carcinomas (ACCs) present an immature pattern of steroidogenesis, dominated by steroid hormone precursors. Modern mass spectrometry-based assays can generate multi-steroid metabolite profiles in urine collections, which can detect differences between ACCs and benign adrenocortical adenomas (ACAs). This review summarizes the promising results of studies which have applied steroid metabolite profiling in biological fluids as a novel diagnostic tool for patients with adrenal tumors, as well as the challenges and limitations of this approach. It also discusses the potential role of steroid profiling as a biochemical surveillance tool to detect recurrence in patients who have undergone resection of an ACC.