BackgroundTime to sustained seizure frequency reduction can provide clinically meaningful epilepsy outcomes.Aims of the StudyTo examine the time course of brivaracetam (BRV) efficacy in adults with focal seizures and focal to bilateral tonic‐clonic seizures (FBTCS).MethodsPost hoc analysis of data pooled from three randomized controlled trials of oral adjunctive BRV in adults with epilepsy. Patients with focal epilepsy and a subpopulation with FBTCS receiving BRV 50, 100, or 200 mg/d (initiated without up‐titration) or placebo for 12 weeks were analyzed for time to sustained ≥75%, ≥90%, and 100% seizure reduction without interruption from first day until trial ends.ResultsEvaluation included 1160 patients with focal seizures, including 352 patients with FBTCS. Sustained ≥75%, ≥90%, and 100% response in focal seizures was higher from day 1 for BRV 100 and 200 mg/d vs placebo (P < .01). Sustained ≥75% and 100% FBTCS reduction from day 1 was higher for BRV 100 and 200‐mg/d groups vs placebo (P < .01).ConclusionsThe majority of patients achieving 75%‐100% sustained seizure frequency reduction (all focal seizure types and the subpopulation with FBTCS) with oral BRV (100 or 200 mg/d) achieved this response on the first‐treatment day.