ABSTRACT Background. The oral cavity is an inseparable part of the human body. The oral cavity is composed of a structure that is a unitary function known as mastication, such as the teeth, tongue, while mucosa known as the stomatognathic system. One part of the oral cavity, namely the tongue, is an organ that has a central function for taste and taste of various types of food flavours and other substances that will enter the body through the oral cavity. However, sometimes the tongue is coated with a thin white layer containing bacteria, desquamated epithelial cells, leukocytes, blood metabolites, and various other components. Purpose: of this study was to determine the relationship between the level of knowledge and the habit of brushing the tongue in coated tongue patients who come to the Dental and Oral Hospital of Universitas Airlangga, Method. This study was descriptive analytic with the type of study was cross sectional. Results: were 28 patients with a good level of knowledge, 11 patients with a moderate level of knowledge, and 2 patients with a bad level of knowledge, and the results were 12 patients with a good level of habits, and 29 patients with a bad habit level. Conclusion. Good level of knowledge about tongue hygiene does not make a good habit also in keeping the tongue clean.