Thyroid cancer is the most common malignant endocrine tumor, with significant morbidity and mortality. Bovine myeloid antimicrobial peptide 28 (BMAP-28) is a cathelicidin that is found in bovine neutrophils. In the present study, the effect and relative mechanism of BMAP-28 on the human thyroid cancer TT cell lineandwere investigated. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, flow cytometry and a TT-xenograft mouse model were used in this study. The data obtained indicated that BMAP-28 significantly inhibited the proliferation of the TT cells. In addition, the Annexin V-fluorescein isothiocyanate/propidium iodide assay detected that BMAP-28 induced apoptotic effects in the TT cells. Moreover, the expression of activated caspase-3 and -9 was upregulated at the transcriptional and translational levels. Simultaneously, the expression of matrix metalloproteinase (MMP)3 and MMP9 was downregulated following BMAP-28 treatment. Finally, BMAP-28 significantly prevented the tumor growth in the TT-xenograft mouse model. These results indicated that BMAP-28 could be a potential agent for the treatment of thyroid cancer.