Despite many breast cancer (BC) survivors turning to the internet for online health information (OHI)1 and the American Medical Association recommending OHI written at the sixth-grade reading level to increase accessibility,2 OHI quality and readability are variable.1 Inaccurate or overly complex OHI can negatively affect patients’ care-seeking and treatment decisions.1 As adverse effects constitute common online queries,1 we assessed the quality and readability of OHI that patients may encounter when seeking information on adverse effects of BC treatment.