<p>Chronic invasive mucormycosis is an uncommon form of invasive fungal sinusitis characterized by a slow and indolent pathogenesis. Unlike the acute fulminant form, it may occur in immunocompetent individuals and present with atypical features, resulting in delayed diagnosis. We report the case of a 36-year-old immunocompetent male who presented with progressive left-sided proptosis of six months duration associated with watering of the eye and conjunctival congestion. Restriction of ocular movements developed over the previous month, while visual acuity remained preserved. The patient had no significant medical comorbidities, although a history of facial trauma one year earlier was reported. Ophthalmological examination revealed proptosis, lower lid retraction, conjunctival congestion, restricted superior and medial rectus movements, and grade II optic disc edema. CT scan of the paranasal sinuses demonstrated irregular opacification of the left maxillary sinus with erosion of the lamina papyracea and orbital extension. The patient underwent endoscopic sinus surgery with orbital decompression. HPE examination revealed chronic granulomatous fungal sinusitis, and Lactophenol Cotton Blue staining demonstrated broad aseptate hyphae with right-angle branching, confirming mucormycosis. This patient was treated with surgical debridement and intravenous Liposomal Amphotericin B and maintenance with oral Posaconasole.This case highlights the importance of considering chronic invasive mucormycosis in the differential diagnosis of slowly progressive unilateral proptosis, even in immunocompetent patients with minimal sinonasal symptoms. Early radiological evaluation, tissue diagnosis, and timely surgical management are essential for preventing vision-threatening and potentially life-threatening complications.</p>