This research communication paper addresses the hypothesis that the use of therapeutic alternatives for mastitis, such as intramammary ozone, can cure the disease with lower costs and without harmful residues for human consumption and without formation of microbial resistance like the ones caused by indiscriminate use of antibiotics in dairy farms. The study was performed in 36 mammary quarters from 12 dairy cows with subclinical mastitis grade three. The experimental units were randomly assigned into four groups and each group received a treatment. Treatments comprised (a) 20 μg/ml ozone gas; (b) 40 μg/ml ozone gas; (c) negative control treatment of 12.5 μg/ml ozonated saline and (d) positive control treatment of 100 mg of cephalexin + 100 mg of neomycin + 10 mg of prednisolone, all by intramammary injection. In all quarters, milk was collected before and after the application of treatments for California mastitis test and evaluation of milk composition, somatic cell count, and bacterial cultures. The results indicated that the use of intramammary ozone did have a therapeutic effect, and whilst this was less than that of antibiotics, ozone does confer some advantages. Treated milk had a good composition, the treatment cost was low, milk withdrawal may not be necessary and there is no risk of antibiotic resistance.