Studies have shown improved tolerability with once-weekly versus three-weekly docetaxel in the second-line treatment of advanced non-small cell lung cancer (NSCLC). This study aimed to evaluate the tolerability of nintedanib plus weekly docetaxel in patients with NSCLC. This phase I, open-label, dose-escalation study (NCT02668393) enrolled patients with locally advanced/metastatic adenocarcinoma NSCLC that had progressed on first-line platinum chemotherapy. The primary endpoint was to determine the maximum tolerated dose of nintedanib (up to 200 mg twice daily BID) combined with weekly docetaxel (35 mg/m.sup.2) on days 1, 8, and 15 based on the occurrence of dose-limiting toxicities (DLTs) over a 28-day treatment cycle. Adverse events (AEs) were also evaluated. The trial terminated prematurely due to recruitment challenges. At termination, seven patients had received nintedanib 150 mg BID and seven nintedanib 200 mg BID, in combination with weekly docetaxel. In the first treatment cycle, DLTs were reported for 1/6 evaluable patients (16.7%) in each group. The disease control rates were 57.1% and 42.9%, respectively. Grade greater than or equal to3 treatment-related AEs affected three patients in each group (42.9%); neutropenia was reported in one patient (14.3%) in each group. Treatment-related serious AEs were reported in three patients (42.9%) receiving nintedanib 150 mg, and two patients (28.6%) receiving nintedanib 200 mg. Overall, nintedanib plus weekly docetaxel was well-tolerated in patients with locally advanced or metastatic lung adenocarcinoma who progressed on first-line platinum-based chemotherapy, without loss of efficacy. DLTs were manageable.