Objectives: The objective of the present study was to observe the effects of 50 Hz magnetic fields (MFs) on the immune function of splenic lymphocytes in mice. Material and Methods: Twenty male Kunming mice (6 weeks old), weighing 18– 25 g, were randomly divided into sham exposure (N = 10) and 500 μT MFs (N = 10) groups. The mice in the MFs group were exposed to 500 μT MFs for 8 h daily (5 days/week) for up to 60 days. In vitro study was carried out to examine the effects of 50 Hz MFs on the expression of inflammatory factor genes and a cluster of differentiation 69 (CD69) in mouse prime splenic lymphocytes activated by para-Methoxyamphetamine (PMA) and ionomycin. In the in vitro experiments, lymphocytes were isolated from the spleen of 10 healthy Kunming mice, the cells were cultured in the Roswell Park Memorial Institute 1640 medium (RPMI-1640) and exposed to 0 μT, 250 μT, 500 μT, or 1 mT MFs in an incubator under 5% carbon dioxide (CO₂) at 37°C for 6 h. The levels of interleukin-2 (IL-2), IL-4, interferon-gamma (IFN-γ), GATA binding protein 3 (GATA-3) and T cell-specific T-box transcription factor (T-bet) were assessed by the real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR), respectively. The expression of CD69 was checked using the flow cytometry. Results: Under our experimental conditions, body weight of the mice exposed to occupational, extremely low frequency- electromagnetic fields (ELF-EMFs) significantly decreased on day 20 and day 30. There were no significant changes observed in vivo in spleen weight, splenic coefficient, splenic histology profile and cytokine production in spleen tissues. Our in vitro experiments showed that 50 Hz MFs had no effect on the expression of these genes and CD69 to primary splenic cells. Conclusions: In conclusion, under the applied experimental conditions, occupational exposure to 50 Hz magnetic field did not alter responses of inflammatory genes and activation of splenic lymphocytes in mice, except for body weight.