Hypertension is one of the leading causes of death in the world. Hypertension can cause complications in the form of coronary heart disease, heart attack (blockage of blood vessels causing tissue damage), heart disease (54%), stroke (36%), and kidney failure (32%). Based on the World Health Organization (WHO) and the International Society of Hypertension (ISH), there are 600 million people with hypertension worldwide, and of which 3 million die every year. The subject of this research is an Expert System in Diagnosing Hypertension. This research starts from January 2021 to May 2021, located at the Regional General Hospital dr. Hasri Ainun Habibi. Based on the results of research and testing that has been carried out, it indicates that the expert system for diagnosing hypertension using the certainty factor method works as expected. The application of the certainty factor method for diagnosing hypertension has been successfully identified. The design of an expert system to diagnose hypertension using the certainty factor method is still far from perfect. To build a perfect system, of course, it is necessary to do further development, both in terms of benefits and in terms of system work.