Introduction: By analyzing the national parameterization of the Nursing Practice Support System, it was found that occupational health nursing has no representation in the current information systems in use, being urgent to structure the existing knowledge in this area. Objectives: Having as client the person in the work context, the intention was to formally represent the knowledge currently available in three classes of nursing information items that represent the critical elements of the decision-making process: i) data resulting from the assessment of the client, ii) diagnoses and iii) interventions. Methodology: This work originates from a global project developed by the Centre for Information Systems Research and Development of Porto Nursing School (CIDESI-ESEP), in collaboration with the Ordem dos Enfermeiros, which was consolidated in the construction of a Nursing Ontology (NursingOntos). For its conception, a qualitative study of inferential nature was carried out, with content analysis of the national parameterization and literature review. For content validation, a focus group was used. Results: Sixty-four items of information were identified, organized by domains, referring to work activity, occupational exposure and health-seeking behaviors: twenty-one data items, with about fifty specifications; ten nursing diagnoses; and thirty-three interventions. The care conception is centered on aspects that are part of the adaptive process of the client in a work environment, namely the awareness as a property, and knowledge and meaning as facilitating or inhibiting conditions of his transition. Conclusions: The Nursing Ontology is a fundamental resource in the backend of the development of nursing information systems, supporting the description of care and the decision-making process. Having as client the person in the work context, it was verified the centrality in the identification of data characterizing the physical intensity and exposure to risk factors of the work activity, and in the adaptive process related to areas that will influence the choice of behaviors that promote his health.