Background: Sinonasal undifferentiated carcinoma (SNUC) is an exceedingly rare head and neck malignancy. No consensus exists on treatment for metastatic disease. Case: A 56-year-old female was diagnosed with SNUC after endorsing sinus congestion, diplopia, and right orbital pain. Initially treated with surgery and radiation, she later developed significant metastatic disease. She demonstrated progression of her hepatic metastases under pembrolizumab therapy. However, the addition of ipilimumab and an IDO1 inhibitor resulted in significant improvement in her lesions as well as an ongoing durable response. Her regimen was complicated by immune-related adverse events successfully treated with steroids. Conclusion: Dual checkpoint inhibition deserves consideration when treating metastatic SNUC, especially after single agent therapy has failed. The positive effect of this treatment may be augmented by IDO1 inhibition.