The aim of this study was to present a case of chronic blepharoconjunctivitis due to Demodex infestation. A 46-year-old man patient presented with itching, burning, tearing, and redness in the right eye for 4 months. Biomicroscopic examination revealed chemosis, hyperemia, and papillary reaction in the right eye. Demodex in the hair follicles of eyelashes and their potential influence were suspected. For diagnosis, lash sampling with direct microscopic counting method was used. When Demodex infestation was diagnosed tea tree oil (TTO) treatment was started. However, TTO increased ocular allergy. After TTO was stopped, topical ivermectin treatment was started. Dramatic improvement was observed in 1 week. No recurrence was seen at 6 months follow-up. Rare causes should be considered in the selection of diagnosis and treatment in long-term unilateral conjunctivitis. Demodex infestation is often overlooked in the differential diagnosis of ocular surface diseases. Topical ivermectin was effective in the treatment of demodex.Keywords: Blepharoconjunctivits, Demodex; ivermectin; tea tree oil.