Azithromycin (AZM), a macrolide antibiotic, has attracted considerable attention for its immunomodulatory and anti-inflammatory properties beyond its traditional antimicrobial use. This review examines the effects of AZM on key immune cells, including B cells, T cells, and natural killer (NK) cells, and its potential applications in the treatment of autoimmune and chronic inflammatory diseases. AZM affects the mammalian target of the rapamycin (mTOR) pathway in T cells, inhibiting proliferation and cytokine production, while also modulating B-cell responses through pathways such as NF-κB and CD27, which affect antibody production. AZM reduces cytotoxicity and cytokine secretion in NK cells without impairing cell viability. The effect of this drug on immune responses to vaccinations, particularly by dampening antibody titers, raises important clinical considerations. While AZM holds promise in managing immune-related conditions such as graft-versus-host disease and asthma, the variability in its effects underscores the need for further research. Understanding these mechanisms will allow for better application of AZM's immunomodulatory potential and mitigation of possible adverse effects on immune function.