PURPOSE Patients with advanced penile squamous cell carcinoma have a poor prognosis (21% 2-year overall survival [OS] from diagnosis). We assessed the activity of atezolizumab (anti–PD-L1) in patients with advanced penile cancer, with or without radiotherapy (RT). PATIENTS AND METHODS A single-center, nonrandomized phase II study with two treatment arms was conducted in 32 patients with histologically confirmed advanced penile cancer. All patients received atezolizumab (1,200 mg) once every 3 weeks. Twenty patients, who were expected to benefit from RT for locoregional disease control, received additional irradiation. The primary end point was 1-year progression-free survival (PFS) for the complete cohort and was reached if the actual 1-year PFS was at least 35%. Secondary end points included OS, objective response rate (ORR), and tolerability. Exploratory biomarker analyses were conducted in pretreatment specimens. RESULTS Median follow-up was 29.1 months (IQR, 18.1-33.5). Grade 3-4 a