Antiviral resistance frequently complicates the treatment of herpes simplex virus (HSV) infections in immunocompromised patients. Here we present the case of an adolescent boy with dedicator of cytokinesis 8 (DOCK8) deficiency, who experienced recurrent infections with resistant HSV-1. We used both phenotypic and genotypic methodologies to characterize the resistance profile of HSV-1 in the patient and conclude that genotypic testing outperformed phenotypic testing. We also present the first analysis of intrahost HSV-1 evolution in an immunocompromised patient. While HSV-1 can remain static in an immunocompetent individual for decades, the virus from this patient rapidly acquired genetic changes throughout its genome. Finally, we document a likely case of transmitted resistance in HSV-1 between the patient and his brother, who also has DOCK8 deficiency. This event demonstrates that resistant HSV-1 is transmissible among immunocompromised persons.