BACKGROUND: Ergonomics is increasingly gaining ground in projects in the energy sector, as well as in the continuous process industry, although the discipline is still framing its space in this milieu. This issue emerges from the designers’ lack of familiarity with ergonomics work, especially in engineering design projects, combined with the usual expectations of organizations regarding the participation of ergonomists and the deliverables they ought to develop throughout the project. OBJECTIVE: This study aims to report the participation of a team of ergonomists in an oil platform basic design, discussing ergonomics structuring as an emerging design discipline. METHODS: This qualitative study used participant observation as a methodology approach aligned with the theoretical framework of Activity Ergonomics (AE). The data collection occurred between October 2018 and June 2020 in Rio de Janeiro, Brazil. RESULTS: The results show the challenges faced by the ergonomics team and strategies adopted in order to create technical specifications (TS), which will determine the work conditions in the future platforms. An evolution in relation to the practice of Ergonomics during this project can be pointed out, even though part of its scope of action remains to be better understood among the design team. CONCLUSION: Considering oil platform project contexts, this work highlights how ergonomics can help integrate the different rationalities that compose the design process.