Background: Perioperative hemodynamic instability is one of the most common adverse events in patients undergoing adrenalectomy for pheochromocytoma. The aim of this study was to analyze the impact of perioperative severe hemodynamic instability. Methods: We present a retrospective, single-center analysis in a major tertiary hospital of all consecutive patients undergoing elective adrenalectomy from 2005 to 2019 for pheochromocytoma. Severe perioperative hypertension and hypotension were evaluated, defined as changes in blood pressure larger than 30% of the preoperative patient-specific mean arterial pressure (MAP). Results: Unilateral adrenalectomy was performed in 67 patients. Intraoperative episodes of hemodynamic instability occurred in 97% of all patients (n = 65), severe hypertension occurred in 24 patients (36%), and severe hypotensive episodes occurred in 62 patients (93%). Patients with more than five severe hypotensive episodes (n = 29) received higher preoperative alpha-adrenergic blockades (phenoxybenzamine 51 ± 50 mg d−1 vs. 29 ± 27 mg d−1; p = 0.023) and had a longer mean ICU stay (39.6 ± 41.5 h vs. 20.6 ± 19.1 h, p = 0.015). Conclusion: Intraoperative hypotensive, rather than hypertensive, episodes occurred during adrenalectomy. The occurrence of more than five hypotensive episodes correlated well with a significantly longer hospital stay and ICU time.