Khat is found in the large shrub, which consists of cathinone. It is the main active ingredient in khat leave responsible for physical and psychological health effects. Khat addiction becomes the growing public health concern in Ethiopia. It is therefore important for individuals to have adequate knowledge of physical and psychological disorder related to khat addiction to avoid the risk. Experts systems are rapidly growing technology and an active area of research in disease diagnosis and treatment. Fuzzy logic is one of the approach used for enhancing personal health care delivery in the health sector. Since there is shortage of experts in the domain area, we develop fuzzy expert system to diagnose the risk of physical and psychological disorder related to khat addicted addiction. A java library (JfuzzyLogic) running on android operating system was used to develop the inference engine and knowledgebase. The source of data to build expert system were collected from literatures, interview with experts and medical data extracted from khat addicted patients with physical and psychological disorder from Felege Hiwote Referral Hospital, Bahir Dar Ethiopia. The designed fuzzy expert system is used for patients and physicians to examine the risk level of the disease. The experimental result showed that the designed expert system performs 95% accuracy. This fuzzy expert system was evaluated and provide effective result for diagnosing physical and psychological disorder related to khat addiction.