Abstract Background Autism spectrum disorder (ASD) is a chronic neurodevelopmental condition with a prevalence rate above 1%, characterized by deficits in social communication and interaction; restrictive, repetitive patterns of behavior, interests, or activities; and a preference for sameness and routines. The majority of adult ASD patients suffer from comorbid conditions such as depression and anxiety. Therapy options for adult ASD patients are lacking, with presently no available evidence-based interventions in Germany. Recently, two interventions to improve social responsiveness have been published. FASTER (“Freiburger Asperger-Spezifische Therapie für ERwachsene” = Freiburg Asperger-specific therapy for adults) is a manualized group psychotherapy program including three modules on psychoeducation, stress regulation management, and non-verbal and verbal social communication training with videotaped tasks. SCOTT&EVA (“Social Cognition Training Tool”, and its enhancement “Emotionen Verstehen und Ausdruecken” = understanding and expressing emotions) is a computer-based training program to enhance social cognition including video and audio material of emotional expressions and complex real-life social situations. Initial studies for both programs have shown good feasibility and efficacy. Methods Three hundred sixty adult participants with an autism spectrum disorder (ASD) will take part in a randomized controlled three-armed multi-center trial to prove the efficacy of manualized group psychotherapy and a manualized computer-based training program. Both interventions will be compared with a treatment as usual (TAU) group, aiming to establish evidence-based psychotherapy approaches for adult individuals with ASD. The primary outcome is evaluated by parents, spouses, or others who have sufficient insight into the respective participant’s social communication and interaction, and will be measured with the Social Responsiveness Scale. First, each of both interventions will be compared to TAU. If at least one of the differences is significant, both interventions will be compared against each other. The primary outcome will be measured at baseline (T0) and 4 months after baseline (T1). Discussion The trial is the first to validate psychiatric therapeutic and training interventions for adult ASD patients in Germany. A trial is needed because the prevalence of ASD in adulthood without intellectual disability is high, and no evidence-based intervention can be offered in Germany. Trial registration German Clinical Trial Register DRKS00017817 . Registered on 20 April 2020.