The differential diagnosis of acute stroke is often a challenge for the emergency care staff. In medical literature, about 30% of patients presenting in an emergency department with suspected stroke at initial assessment are actually stroke mimic. We report here a case of a 61-year-old woman who got admitted at the emergency service for an acute stroke that was actually a symptomatic hyponatremia due to a Schwartz-Bartter syndrome associated with an undiagnosed breast cancer. It is very important to quickly identify and manage patients presenting with a high probability of acute stroke even though many other pathological conditions can present with the same clinical onset. Electrolyte disturbances are one of those stroke mimic conditions that are usually reversible if properly identified and treated on time.