This study investigated the knowledge and attitudes of Jordanian school counselors toward diabetes mellitus. A sample of 295 counselors completed a questionnaire consisting of two parts concerning knowledge and attitudes. The face validity of the questionnaire was assessed using an informed panel of judges, and its reliability was established using the test- re-test method. Results showed that counselors as a whole had a moderate level of knowledge about diabetes. This level of knowledge was related to counselor gender (females were more knowledgeable than males) and to knowing a person with diabetes, but not to counselor age. Results also showed that counselors showed favorable attitudes toward students with diabetes. Knowing a student with diabetes had no influence on attitudes.