Background. Adrenal collision tumors (ACTs), in which distinct tumors coexist without intermingling in the same adrenal gland, are rare and their actual prevalence is unknown. ACTs commonly consist of adrenal cortical adenoma, pheochromocytoma, or metastatic malignant tumor. Case Report. A 32-year-old woman who had been experiencing gastric discomfort for one month was referred to our hospital with abnormal imaging findings. The physical examination and the laboratory data including endocrine studies were unremarkable. Abdomen computed tomography (CT) and magnetic resonance imaging (MRI) showed two adjacent masses in the left suprarenal fossa, and a laparoscopic left adrenalectomy was done. Histological and immunohistochemical (IHC) examinations revealed two distinct tumors: a pigmented adrenal cortical oncocytoma (ACO) and a ganglioneuroma, respectively. Conclusion. Both tumors are rare in the adrenal gland and exist as ACTs only exceptionally rarely. This is the first reported case of coexisting oncocytoma and ganglioneuroma in the same adrenal gland to our knowledge.