Purpose: To evaluate the 1-year safety of lifitegrast ophthalmic solution 5.0% in patients with dry eye disease compared with placebo. Methods: SONATA (Safety Of a 5.0% coNcentrATion of lifitegrAst ophthalmic solution) was a multicenter, randomized, prospective, double-masked, placebo-controlled phase 3 study (NCT01636206). Adults (≥18 years) with dry eye disease (Schirmer test score ≥1 and ≤10 mm; corneal staining score ≥2.0) were randomized 2:1 to lifitegrast ophthalmic solution 5.0% or placebo twice daily for 360 days. The primary objective was percentage and severity of treatment-emergent adverse events (TEAEs). Secondary objectives were ocular safety measures: corneal fluorescein staining, drop comfort, best-corrected visual acuity, slit-lamp biomicroscopy, and intraocular pressure over 7 visits. Exploratory objectives included concentration of lifitegrast in plasma. Results: The safety population comprised 331 participants (220 lifitegrast; 111 placebo). There were no serious ocular TEAEs. Overall, 53.6% of participants receiving lifitegrast experienced ≥1 ocular TEAE versus 34.2% in the placebo group; most TEAEs were mild to moderate in severity. Rates of discontinuation because of TEAEs were 12.3% (lifitegrast) versus 9.0% (placebo). The most common (>5%) TEAEs occurring in either treatment group were instillation site irritation (burning), instillation site reaction, visual acuity reduced, dry eye, and dysgeusia (change in taste). Ocular safety parameters for lifitegrast were similar to placebo. The mean plasma lifitegrast concentration at 360 days (n = 43) was below the limit of detection. There was no indication of systemic toxicity or localized infectious complications secondary to chronic immunosuppression. Conclusions: Lifitegrast ophthalmic solution 5.0% seemed safe and well tolerated in this study, with no unexpected adverse events.