In this study, it was aimed to determine the therapeutic efficiency of Corynebacterium cutis lysate that is a nonspecific immunostimulant in cows with subclinical mastitis. The study material was 88 udder lobs with subclinical mastitis of cows from different breeds and age (4-7 years) based on the same farm. Subclinical mastitis was diagnosed by microbiological tests, California Mastitis Test (CMT) and Somatic Cell Count (SCC). 10 ml of Corynebacterium cutis lysate was injected subcutaneously to the animals which were diagnosed with subclinical mastitis. After 15 days from the injection microbiological tests, CMT and SCC determinations were performed in the same udder lobs. Additionally, milk samples were taken from the said udder lobs before and after Enzyme-Linked Immunosorbent Assay (ELISA) determined immunoglobulin G (IgG) concentrations. CMT positivity rates, SCC and IgG levels before and after Corynebacterium cutis lysate injections were 100% and 63.63%; 897.470 and 923.780 cell/ml; 845.11 and 887.27 mg/ml, respectively. The microbiological growth rates before and after the applications were found to be 13.63% and 22.73%, respectively. The obtained data showed that, although not statistically significant, microbiological growth rates and SCC were increased after Corynebacterium cutis lysate application to the cows with subclinical mastitis. However, it was observed that the milk IgG levels were increased significantly after the application. These results may indicate the use of Corynebacterium cutis lysate applications as a supportive treatment to enhance the resistance in cows against subclinical mastitis.