Gastrointestinal stromal tumors (GISTs) are rare neoplasms of the gastrointestinal (GI) tract. The occurrence of these neoplasms ectopically outside the GI tract is extremely uncommon. Only one case of primary adrenal GIST has been reported in the literature. In this account, we report a second case of primary adrenal GIST in a 34-year-old male who presented with a 5-week history of gradually progressive left flank pain and early satiety. Whole-body positron emission tomography (PET)/computed tomography (CT) scan showed a 14 × 11 cm hypermetabolic (18)fluorodeoxyglucose (FDG)-avid mass lesion involving the left adrenal gland and dorsal part of the left hemi-diaphragm. Biopsy of the lesion revealed tumor cells that are immunoreactive to CD-117 and CD-34 and negative to CD-31, S-100, cytokeratin, desmin, and vimentin, features characteristic of GIST. The patient was given imatinib, which drastically decreased his complaints with almost complete resolution of the tumor on his last follow-up radiographic images. Primary left adrenal GIST is an extremely rare neoplasm and can be confused with GISTs arising from the greater curvature of the stomach. Imatinib therapy is optimal in the management of these tumors.