Integration of locoregional therapies such as stereotactic body radiation therapy (SBRT) is increasing in the treatment of hepatocellular carcinoma (HCC), the most common primary cancer of the liver. A 68-year-old man with hepatitis C was diagnosed with American Joint Committee on Cancer stage 2 (cT2N0M0), Child-Pugh class A, multifocal HCC. He completed adaptive MR-guided stereotactic body radiation therapy (MRgSBRT) for a total dose of 50 Gy in 5 fractions. At the 3-month follow-up, a three-phase abdominal CT showed a decrease in the size of the treated lesion and a new gastric fistula was noted. He started a proton pump inhibitor and remained under close observation. At the 6-month follow-up, imaging showed a decrease in tumor size with continued evidence of a contained fistula. Severe side effects are possible following MRgSBRT to the liver, even with the utilization of adaptive treatment, highlighting the importance of attention to high-dose isodose lines near normal tissues and adherence to dose constraints.