Gastrointestinal perforation is a well-addressed complication of exogenous hypercortisolism; however, patients with endogenous Cushing's syndrome (CS) do not usually experience this condition in clinical practice. The literature on this subject is limited and consists solely of clinical case reports/series with only 23 instances of gastrointestinal perforation occurring in individuals with endogenous Cushing's syndrome. This is mainly attributed to the rarity of Cushing's syndrome itself and the low chance of occurrence of such complications. We report a case of a recently diagnosed adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome in a 30-years-old female who presented initially with a three-month history of progressive weight gain, generalized weakness, acne, menstrual irregularity, and severe hypokalemia, and then developed a gastric ulcer perforation only one month after her ACTH-dependent Cushing's syndrome diagnosis and was managed through emergent surgery.