ROS proto-oncogene 1 (ROS1) encodes a type I integral membrane protein with tyrosine kinase activity and whose activating alterations are involved in the aggressiveness of several tumor types. Fusions involving ROS1 gene are present in 1–2% of lung adenocarcinomas and other solid tumors. Entrectinib, also known as RXDX-101, is a potent second-generation, multitarget oral inhibitor against NTRK1, NTRK2, NTRK3, ALK, and ROS1 with the ability to cross the blood–brain barrier. Results of Phase I and II trials have led the Food and Drug Administration to grant approval to entrectinib for the treatment of patients with metastatic, ROS1-positive non-small cell lung cancer (NSCLC). In this review, we will describe the biology of ROS1, as well as results of the efficacy and safety of different clinical trials evaluating entrectinib in ROS1-positive NSCLC.