Breast cancer is the most prevalent form of tumor worldwide and the leading cause of cancer among women globally. Similarly, mammary tumors are also common in canines, with a majority of them unfortunately being malignant. While chemotherapy is one of the most frequently employed treatments, it often comes with significant side effects. Consequently, alternative therapies are under investigation, including oncolytic viruses. The Newcastle disease virus (NDV) stands out due to its capacity to selectively target and destroy tumor cells while preserving healthy tissue, as well as its ability to trigger a robust antitumor immune response. Numerous studies support the utilization of NDV in treating various cancer types, ranging from brain tumors to gastrointestinal tract neoplasms. Other researches have also yielded promising results in the treatment of mammary neoplasms. This review aims to compile information about NDV and its application in oncolytic virotherapy for the study and treatment of human breast cancer and canine mammary tumors, employing cell lines, animal models, and clinical trials.