With a very low incidence (1-4 cases per 1 million per year), characterized by insulin hypersecretion, independent of the glycemia control system, insulinoma is a rare endocrine tumor, clinical with accentuated neuropsychological symptoms that hampers clinical diagnosis. We present a case of a 33 years old patient with no notable personal history, active lifestyle, non-smoker, a work environment that doesn’t involve professional toxicity; a remarkable family history of a brother with type 1 diabetes mellitus and grandmother with liver adenocarcinoma was noticed; in this particular case Whipple triad was strongly suggestive, gastrointestinal upper-ultrasonography endoscopy with tissue puncture as a tumor diagnostic tool was used and laparotomy was used successfully for removing the tumor, with favorable follow-up.