Summary: The immune system is influenced by vitamin B complex including vitamin B1, B6, and B12. The B complex insufficiency can cause significant impairment in cellular and immune function and trigger an inflammatory response. Strengthening the immune system with B vitamins could go a long way in preventing and treating COVID-19 patients. B-Complex vitamins play a significant role in activation of adaptive and inborn immune responses, reduction of cytokine levels such as proinflammatory cytokines, reduction of oxidative stress, preservation of endothelial homogeneity, improving pulmonary function, prevention of hypercoagulable conditions and shortening the length of hospital stay. Thus, the role of B complex in patients with COVID-19 needs to be further evaluated.