This paper discusses the development of an expert system for diagnosing depression using CLIPS. Depression is a prevalent mental illness globally, affecting approximately 3.8% of the population. Depression is also a leading cause of suicide, which is the second leading cause of death among young people. Diagnosing depression is challenging as there is no clear objective indicator to diagnose it. The expert system is built using knowledge acquired from analyzes patient answers to diagnose depression. The expert system aims to provide an affordable and applicable method for diagnosing depression.