Background: Thyroid hormones play a pivotal role in the metabolism of human body. Changes of the thyroid gland activity manifest in nearly all body systems. Appropriate knowledge of the public about thyroid disorders and their manifestations is essential for early detection. Objective: The aim of this study was to assess public knowledge regarding the differences between hyperthyroidism and hypothyroidism in Tabuk city, Saudi Arabia. Methods: A cross sectional study was conducted on 300 randomly selected adult residents in Tabuk city. An Arabic self-administered questionnaire was filled by the participants through a link or softcopy. The questionnaire included questions about socio-demographic data of the respondents and other questions to assess knowledge about the type and functions of thyroid gland, its disorders, factors affecting thyroid disorders, and their common manifestations. Results: Respondents with good knowledge of thyroid gland and its disorders constituted 52%, while 45% had poor knowledge. Good knowledge was demonstrated in questions about the type of thyroid gland (71.4%), and the most susceptible individuals to have the disorder (90.4%). Manifestations of hypothyroidism were also recognized by most respondents, particularly weight gain (76%) as well as fatigability and sleepiness (74.9%). Inadequate and poor knowledge was found as regards the functions of thyroid gland, causes of thyroid hormonal disturbances, and symptoms of hyperthyroidism. Conclusion: The knowledge of respondents about thyroid disorders is poor. Inadequate knowledge can result in increased number of undetected cases. Health education should be launched by the health authorities and distributed through all available channels of information. Good knowledge of the general population about thyroid disorders is expected to decrease the incidence of preventable disorders and increase the detection of subtle undiagnosed cases.