Background: The coconut tree (Cocos nucifera) is a member of the palm tree family (Arecaceae) and the only living species of the genus Cocos, can refer to the whole coconut palm, the seed, or the fruit, which botanically is a drupe, not a nut. The term is derived from the 16th-century Portuguese and Spanish word coco meaning "head" or "skull" after the three indentations on the coconut shell that resemble facial features. Objectives: The main goal of this expert system is to get the appropriate diagnosis of disease and the correct treatment by presenting suggestions on coconut diseases to the user with pictures to be accurately diagnosed. Methods: in this paper the design of the proposed Expert System which was produced to help farmers in diagnosing many of the coconut diseases such as: Bud Rot, Leaf Rot, Stem Bleeding, Tanjore wilt and Root (wilt). the proposed expert system presents an overview about coconut diseases are given, the cause of diseases is outlined and the treatment of disease whenever possible is given out. CLIPS Object Expert System language was used for designing and implementing the proposed expert system. Results: The proposed coconut diseases diagnosis expert system was evaluated by agricultural engineers and they were satisfied with its performance. Conclusions: The Proposed expert system is very useful for agricultural engineer, specialists in plant pathology, and researchers on coconut plant. Keywords: Artificial Intelligence, Expert Systems