ConvitVax is a personalized vaccine for the treatment of breast cancer, composed of autologous tumor cells, bacillus Calmette-Guérin (BCG) and low concentrations of formalin. Previous pre-clinical studies show that this therapy induces a potent activation of the immune system and achieves an effective response against tumor cells, reducing the size of the tumor and decreasing the percentage of immunosuppressive cells. In the present study, we evaluate the toxicity of ConvitVax in healthy BALB/c mice to determine potential adverse effects related to the vaccine and each of its components. We used standard guidelines for pain, discomfort and distress recognition, continuously evaluated the site of the injection, and completed blood and urine clinical tests. Endpoint necropsy was performed, measuring the weight of organs and processing liver, kidney, thymus and lung for histological examination. Results show that the vaccine in its therapeutic dose, at 3 times its therapeutic concentration, and its individual components did not cause death or behavioral or biological changes, including any abnormalities in whole-body or organ weights, and tissue damage. These results support the safety of ConvitVax with minimal to no side-effects.