The SSIS SEL Brief + Mental Health Scales (SSIS SELb+MHS) are multi-informant assessments developed in the United States to assess the social and emotional learning (SEL) competencies and emotional behavior concerns (EBCs) of school-age youth. Although there are translations of the SEL items of the SSIS SELb+MHS available in other languages, a German translation has never been completed and validated, despite the growing need for SEL and mental health assessment in German-speaking countries. To address this need, this study's primary purpose was the examination of a German translation of the assessment with a specific focus on measurement invariance and concurrent validity invariance testing with 821 3rd through 6th-grade students in Austria and Germany. Results indicated that the SELb+MHS items clustered into 2 SEL factors and 2 EBC factors. With regard to measurement invariance, the SELb+MHS functioned similarly across both Austria and Germany and full scalar invariance was achieved. Additionally, the overall pattern of concurrent validity relationships was as expected and similar across countries. Implications and future directions are discussed.