Inflammatory myopathies, including polymyositis (PM), may add risk to electroconvulsive therapy (ECT) due to muscle sensitivity to depolarizing neuromuscular agents. In addition, previously published case series have shown elevations in creatine phosphokinase (CPK), an index of PM disease severity, in patients without muscle disease receiving ECT. We report the case of a 74-year-old female who developed initial onset of depression after steroid treatment for biopsy-proven PM. After she failed to respond to trials of antidepressant medications, she was treated with 21 inpatient and outpatient sessions of ECT over 2 years. Each course of treatment was effective for her depression without worsening symptoms of muscle disease activity. Two previous cases have described the use of ECT in patients with inflammatory myopathies, but our case is the first to report maintenance phase treatment with CPK monitoring.