This work proposes a semi-quantitative risk assessment methodology, which was applied and tested in the Ship Building Industry. It covers a wide range of risks related to occupational accidents in a shipbuilding yard environment, more specifically at Arsenal do Alfeite, a large shipyard in Portugal. The initial qualitative analysis focuses on the bow-tie diagram technique but it also integrates concepts and classifications schemes defined by the Eurostat within the European Statistics on Accidents at Work (ESAW) Project. The structure of the diagram enables the identification of the relevant accident’s causal pathways and their consequences at the same time as it identifies the existing or needed safety barriers. In what concerns the semi-quantitative assessment, the accident risk level and acceptance criteria were established through a scoring system, using national data on accident statistics for the sub-sector: Ship Building & Repairing (code NACE 35.1). The statistical data was supplied by GEP (the Office of Strategy & Planning of the Portuguese Ministry of Labour & Social Solidarity). The authors present and discuss a specific case study, in the shipyard’s technological area of surface treatment and protection, to demonstrate the method’s applicability and usefulness.