Purpose To investigate for the first time the immunohistochemical and mutational status of β-catenin in a mandibular case of adenomatoid odontogenic tumor (AOT) and to review the immunohistochemical expression data of various markers (cytokeratins, metalloproteinases, etc) in such a lesion. Materials and Methods A case of follicular-type AOT in a young male patient was analyzed in regard to the immunohistochemical expression of β-catenin and mutations of the β-catenin gene (CTNNB1). Its expression is altered in some odontogenic tumors. Results We found a strong cytoplasmic expression of β-catenin, but no molecular anomaly within the exon 3 of CTNNB1. β-catenin is considered to play a role in cell differentiation processes. Conclusion Our results were consistent with previous findings in ameloblastoma and malignant odontogenic tumors. However, β-catenin alterations had not been explored in AOT so far. Further studies are necessary to understand the specific regulation of β-catenin in the AOT pathogenesis.