This Phase III, long-term, open-label extension (OLE) trial (EP0009; NCT01832038) was conducted to evaluate the long-term safety, tolerability, and efficacy of adjunctive lacosamide (100-400 mg/day) in Chinese and Japanese people with epilepsy (PWE) (16-70 years) who had completed a double-blind, randomized, placebo-controlled trial of adjunctive lacosamide (EP0008; NCT01710657). PWE entered the OLE trial on 200 mg/day lacosamide and up to 3 concomitant antiseizure medications. Dose adjustments were permitted to optimize tolerability and seizure reduction. Safety variables were treatment-emergent adverse events (TEAEs) and discontinuations due to TEAEs. Efficacy variables were percent change in focal seizure frequency per 28 days from Baseline of the double-blind trial, ≥50 % and ≥75 % responder rates, seizure-freedom, and proportion of PWE on lacosamide monotherapy. Overall, 473 PWE (74.0 % Chinese and 26.0 % Japanese) were enrolled; 238 (50.3 %) PWE completed the trial and 235 (49.7 %) discontinued, most commonly due to lack of efficacy (81 [17.1 %]), adverse events (55 [11.6 %]), and consent withdrawn (49 [10.4 %]). During the trial, PWE received lacosamide for a median of 1016.0 days (∼3 years), with a total exposure of 1454.8 person-years; 321 (67.9 %) PWE received lacosamide for >24 months, and 246 (52.0 %) for >36 months. The median modal dose of lacosamide was 300 mg/day. Overall, 410/473 (86.7 %) PWE reported TEAEs, 244 (51.6 %) had a TEAE that was considered drug-related, and 49 (10.4 %) discontinued due to a TEAE. The most common TEAEs (≥20 % of PWE) were nasopharyngitis, dizziness, and upper respiratory tract infection. The median reduction in focal seizure frequency per 28 days from Baseline was 57.1 %, and the ≥50 % and ≥75 % responder rates were 57.1 % (269/471) and 29.7 % (140/471), respectively. Among PWE who completed 12, 24, and 36 months of treatment, the 12-, 24-, and 36-month seizure-freedom rates were 3.5 % (13/375), 3.4 % (11/321), and 2.0 % (5/247), respectively. Among PWE exposed to lacosamide for ≥6 months and ≥12 months, the proportions of PWE that maintained continuous monotherapy for ≥6 months and ≥12 months were 5.0 % (21/421) and 5.0 % (19/378), respectively. Overall, lacosamide was well-tolerated as long-term adjunctive therapy in Chinese and Japanese PWE and uncontrolled focal seizures, with improvements in seizure reduction maintained over 36 months of treatment.