Gemifloxacin is a broad spectrum antibiotic and has shown excellent coverage against a wide variety of microorganisms. In this study, an attempt was made to evaluate the immunomodulatory potential of gemifloxacin in male swiss albino mice in vivo.Three doses of gemifloxacin 25 mg/kg, 50 mg/kg and 75 mg/kg were used intraperitoneally (IP) for the evaluation of immune responses in mice. Delayed type hypersensitivity (DTH), heamagglutination assay, jerne hemolytic plaque formation assay and cyclophosphamide induced neutropenia assay were performed to evaluate the effect of gemifloxacin on immune responses.DTH assay has shown the significant immune suppressant potential of gemifloxacin at 25 mg/kg dose and 75mg/kg dose. Total leukocyte count (TLC) has shown decrease in leukocyte count (P<0.05) in drug treatment groups before cyclophosphamide administration and significant decrease (P<0.001) in leukocyte count after cyclophosphamide administration as compared to negative control group. Differential leukocyte count (DLC) has shown significant decrease (P<0.001) in percentage count of lymphocytes in 75 mg/kg treatment group in leukopenic mice while increase (P<0.01) in monocytes percentage in 50 mg/kg treatment group in leukopenic mice and increase in neutrophil percentage count (P<0.05) in all treatment groups was observed after cyclophosphamide administration. Humoral immune response is shown to be suppressed in dose dependent manner by both heamagglutination titre values (P<0.001) and jerne hemolytic plaque formation assay (P<0.001).The results of this work clearly demonstrate that gemifloxacin has significant immunomodulatory potential.