Infections are common comorbid conditions in hospitalized patients, including those receiving electroconvulsive therapy (ECT). In this report, we demonstrate the fluoroquinolone class of antibiotics can be associated with prolonged electroconvulsive seizure duration. We describe an 82-year-old woman treated with the fluoroquinolone, moxifloxacin, during a course of ECT. After previously tolerating ECT well, introduction of moxifloxacin for a respiratory tract infection was associated with prolonged seizure duration despite complete resolution of her respiratory complaint. Taken together with other evidence that fluoroquinolones lower seizure threshold, this report suggests fluoroquinolones should be avoided in patients receiving ECT.