PURPOSE: To determine the incidence and clinical features of diffuse lamellar keratitis (DLK) after small-incision lenticule extraction (SMILE). SETTING: Department of Ophthalmology, Eye and ENT Hospital of Fudan University, Shanghai, China. DESIGN: Retrospective case control study. METHODS: Small-incision lenticule extraction for myopia was performed from September 1, 2011, to October 31, 2013. Preoperative clinical characteristics; treatment parameters; and intraoperative and postoperative complications, including the incidence, severity, clinical outcome, and resolution of DLK, were recorded. The independent t test, chi-square test, univariate repeated measures, and multivariate linear regression analysis were used to make statistical comparisons between eyes that developed DLK and those that did not. RESULTS: The study enrolled 1112 eyes (590 patients). Eighteen eyes (1.6%) (11 patients) developed DLK. These patients presented 1 to 3 days postoperatively with mild to moderate inflammation. Thirteen eyes (72.2%) had stage 1 DLK, 4 (22.2%) had stage 2, and 1 (5.6%) had stage 3. After intensive treatment with topical corticosteroids, the stage 1 and stage 2 cases resolved within 3 weeks and the stage 3 case resolved in 1 month. The postoperative corrected distance visual acuity was the same or better than preoperatively in all eyes. There was a statistically significant increase in the incidence of DLK with thinner lenticules (P = .02) and larger diameter lenticules (P = .01), although multifactorial analysis showed lenticule thickness to be the only factor (P = .03). CONCLUSIONS: Diffuse lamellar keratitis is a potential complication after small-incision lenticule extraction, although it had a low incidence. The risk factors for DLK must be further elucidated. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.