Asset health management plays a role in safety, reliability, and cost in the oil and gas industry. Health management requires considering human reliability since it affects asset health. Indeed, human reliability factors are considered carefully during the facility’s design phase but rarely during operation. Therefore, identifying these factors during operation helps to prevent incidents. This article presents research on the impact and role of human reliability in oil and gas operations. Human Reliability Assessment (HRA) methodology is used to understand human error in practice, including human reliability estimation using the Human Error Assessment and Reduction Technique (HEART) and Fault Tree analysis (FTA). A deep investigation of a real case study from Oman’s oil and gas industry, including interviews and questionnaires, is used to prove the concept. The real case study shows a 3.3% human error probability when performing a task of mechanical isolation, 8.8% for the task of de-isolation of override, and 24.8% for the task of managing emergency operations. The study also shows that quantifying human reliability on critical tasks performed by humans can support improvement in systems, governance, and technology to prevent incidents.