Objective This study aimed to investigate the changes of galectin-9, interleukin-4(IL-4) and interferson-γ(IFN-γ) in patients with myocarditis and analyze the clinical significance of these cytokines. Methods Subjects were 93 patients enrolled in our hospital from January of 2014 to December of 2016, 76 with myocarditis, and 30 healthy volunteer adults. Patients with myocarditis were divided into group A (≤30 days, n=49) and B group (>30 days, n=27) according to the course of the disease. Serum concentrations of galectin-9, IFN-γ and IL-4 were detected by an enzyme-linked immunosorbent assay (ELISA). In conclusion, serum galectin-9 could be a new biomarker for patients with myocarditis. Results The levels of serum galectin-9, IFN-γ and IL-4 were higher in patients with myocarditis than those in healthy subjects (P＜0.05). The levels of galectin-9, IL-4 and IFN-γ/IL-4 in group B were significantly lower than those in group A, but still significantly higher than those in normal control group (P＜0.05). Serum galectin-9 was positively correlated with IFN-γ, IL-4, IFN-γ/IL-4, AST, CK-MB, cTnI and LVD, and negatively correlated with the time of onset and LVEF in patients with myocarditis. Conclusion This study showed that serum galectin-9 levels increased in patients with myocarditis, and were positively correlated with IFN-γ, IL-4, IFN-γ/IL-4, suggesting that serum galectin-9 might has potential clinical value in the diagnosis and following-up of myocarditis.