Purpose: Optimal treatment with antiepileptic drugs (AEDs) is an important part of care for brain tumor patients with epileptic seizures. Lamotrigine and lacosamide are both examples of frequently used non-enzyme inducing AEDs with limited to no drug-drug interactions, reducing the risk of unfavorable side effects. This study aimed to compare the effectiveness of lamotrigine versus lacosamide. Methods: In this multicenter study we retrospectively analyzed data of patients with diffuse grade 2–4 glioma with epileptic seizures. All patients received either lamotrigine or lacosamide during the course of their disease after treatment failure of first-line monotherapy with levetiracetam or valproic acid. Primary outcome was the cumulative incidence of treatment failure, from initiation of lamotrigine or lacosamide, with death as competing event, for which a competing risk model was used. Secondary outcomes were uncontrolled seizures after AED initiation and level of toxicity. Results: We included a total of 139 patients of whom 61 (44%) used lamotrigine and 78 (56%) used lacosamide. At 12 months, there was no statistically significant difference in the cumulative incidence of treatment failure for any reason between lamotrigine and lacosamide: 38% (95%CI 26–51%) versus 30% (95%CI 20–41%), respectively. The adjusted hazard ratio for treatment failure of lacosamide compared to lamotrigine was 0.84 (95%CI 0.46–1.56). The cumulative incidences of treatment failure due to uncontrolled seizures (18% versus 11%) and due to adverse events (17% versus 19%) did not differ significantly between lamotrigine and lacosamide. Conclusion: Lamotrigine and lacosamide show similar effectiveness in diffuse glioma patients with epilepsy.