The rearrangement of c-ros oncogene 1 (ROS1) has been recently identified as an important molecular target in non small cell lung cancer (NSCLC). ROS1 rearrangement and epidermal growth factor receptor (EGFR) mutation were mutually exclusive each other in previous studies, and the clinical implication of co-existence of the two genetic alterations has not been determined. We report a case of 46-year-old female never-smoker NSCLC patient whose tumor harbored ROS1 rearrangement and EGFR mutation concomitantly. She had undergone curative surgery for stage IIIA NSCLC, and the recurrence in left pleura and brain occurred at 2 years after the surgery. She received several lines of chemotherapy including docetaxel plus carboplatin, erlotinib, pemetrexed, and gemcitabine. Erlotinib therapy showed a favorable treatment response with progression-free survival of 9.5 months and partial response of tumor on radiologic evaluations. This case represents a successful erlotinib treatment in a NSCLC patient with concurrent ROS1 rearrangement and EGFR mutation.