This book constitutes the proceedings of the 6th International Symposium on Model-Based Safety and Assessment, IMBSA 2019, held in Thessaloniki, Greece, in October 2019. The 24 revised full papers presented were carefully reviewed and selected from 46 initial submissions. The papers are organized in topical sections on safety models and languages; dependability analysis process; safety assessment; safety assessment in automotive industry; AI in safety assessment.