AimsTo evaluate the efficacy, safety, and tolerability of adjunctive lacosamide therapy against focal seizures in young children (1 month – 4 years).MethodsThis non‐randomized, open‐label, and self‐controlled real‐world study included 105 children (1 month–4 years) with focal seizures treated with adjunctive lacosamide therapy at Children's Hospital of Chongqing Medical University.Results(1) The 50% response rates at 3, 6, 9, and 12 months of follow‐up were 58.1%, 61.0%, 57.1%, and 56.2%, while the seizure‐free rates were 27.6%, 34.3%, 32.4%, and 37.1%, respectively. The 50% response rate of the first addition of lacosamide for focal seizures was much higher than the second and later added treatment at 3 months (p = 0.038). After 1 year of follow‐up, these children showed an improvement in neurodevelopmental levels (p < 0.05). (2) Lacosamide retention rate was 72.7% (64/88) after 1 year of follow‐up. Lack of efficacy and serious adverse events were independent risk factors for the lacosamide retention rate. (3) During adjunctive lacosamide therapy, 13 (12.4%) patients reported adverse events and five (4.7%) patients withdrew due to adverse events, including vomiting drowsiness, ataxia (0.94%), neck itching with eczema (0.94%), irritability (1.88%), and gastrointestinal discomfort (0.94%).ConclusionAdjunctive lacosamide therapy was effective, safe, and well‐tolerated in young Chinese children with focal seizures in this study.