Background Lung cancer patients undergoing palliative chemotherapy exhibit many symptoms related to the disease, such as adverse events and infectious complications during treatment, which impacts directly their health-related quality of life (HRQOL). Nutritional status is a relevant aspect among advanced cancer patients under palliative care and food supplementation has the potential to reduce treatment-related adverse effects and improve the nutritional status. The product named AferBio® is a fermented supplement that has been described as able to provide some benefits, including the capacity to potentiate the effects of anticancer drugs, by promoting the reduction of side effects and ultimately improving HRQOL. Methods/design A Phase II double-blind placebo-controlled randomized clinical trial to assess the use of food supplementation with AferBio® in Stage IIIB or IV non-small cell lung cancer (NSCLC) patients beginning a second-line palliative mono-chemotherapy. The primary goal is to compare HRQOL scores between the arms of the study over time. The ten first patients included in the present study will undergo an AferBio®toxicity-testing (non-randomized phase). If no significant toxicity is found, the study will move on to the randomized phase. All patients will be randomized in blocks at a 1:1 ratio using the online tool REDCap. ECOG-PS (0–1 versus 2) criteria will be used for stratification. All patients included in the trial will be evaluated at baseline and at each chemotherapy cycle . Each evaluation will include the following: HRQOL (EORTC QLQ-C30, LC13 and IQualiV-Lung), ECOG-PS, anthropometric measurements, clinical and laboratory toxicity assessment and response evaluation. Discussion During palliative systemic therapy in advanced cancer patients, one of the main goals is the improvement and maintenance of HRQOL, which can be negatively affected by cancer symptoms, cancer- or treatment-related psychosocial difficulties, and chemotherapy toxicity. Thus, much research has been dedicated to the development of new and more effective and/or less toxic cancer therapies. The present study is justified by the testing of a novel food supplement that may reduce some toxicities, thus, having a potential positive impact on the HRQOL of lung cancer patients. The product in question (AferBio®) is already available for sale in Brazil, but has not yet been fully tested in cancer patients. Trial registration This Trial was registered on March 19, 2018 with ClinicalTrials.gov , NCT03469063. Protocol version: 2.0 from March 26, 2018. Trial status: Patient enrollment in the study began in April, 2018.