A 10-year-old Belgian Warmblood gelding, who was an international level jumper, initially presented to Cornell’s Large Animal Surgery service in 2013 for chronic, antibiotic unresponsive nasal discharge and an episode of mild epistaxis from the right nares. Through endoscopic exams, sinus radiograph, and computed tomography (CT) scans, the patient was diagnosed with bilateral progressive ethmoid hematomas (PEH). Over the course of two years, the initial treatment included multiple intralesional formalin injections followed by multiple laser ablation treatments to which the PEH became refractory and eventually recurred and progressed. In 2016, the now 13-year-old gelding returned to Cornell for an episode of left sided epistaxis. A PEH invading the paranasal sinuses and nasal passage was found on CT, which was removed via a frontonasal sinus flap. Just two months later, the patient return for right-sided epistaxis and a CT scan revealed a PEH invading the right sphenopalatine sinus. A surgical approach was devised using a frontonasal trephination to access the sinus with endoscopic guidance via the right nasal passage. Using debridement and lavage, the PEH was successfully removed and the patient has had no recurrence to date.