On June 23, 2021, Hoppus revealed that he was undergoing treatment for cancer after accidentally sharing a picture of himself undergoing chemotherapy treatment to his public Instagram Story. On July 11, he said that he was experiencing stage 4 diffuse large B-cell lymphoma. On September 29, Hoppus announced that he was declared cancer-free, but would continue to be screened every 6 months in case the cancer returns.
