Key Clinical Message Treatment of Pseudomonas aeruginosa remains challenging, despite the availability ceftolozane‐tazobactam. We report a treatment failure with ceftolozane‐tazobactam salvage therapy for pneumonia complicated by lung abscess. Drug resistance, dose selection, and source control are possible contributing factors. Ceftolozane‐tazobactam susceptibility testing should precede therapy and consideration should be given to dosing selection.