Introduction: Lack of adherence to a strict gluten-free diet (GFD) is the main reason for poorly controlled disease in patients with coeliac disease (CD). This study aimed to assess the association between knowledge of CD and its medical diet to the adherence of GFD among adult patients with CD. Methods: A cross-sectional study was carried out with a total of 90 adult patients with CD (aged between 18-65 years). The data collecting instruments were a combination of four questionnaires as follows: assessment of knowledge of coeliac disease (AKCD), gluten-free diet knowledge scale (GFD-KS), coeliac disease adherence test (CDAT), and questions on potential factors influencing GFD adherence among patients. Results: An average knowledge score of five points out of seven was obtained from 46 participants (51%). Mean score for knowledge on gluten-free diet was seven points out of 17 in 59 participants (65%). Adequate adherence to GFD was observed in 56% of the participants. No association was found between knowledge of CD and GFD to the adherence of GFD (p>0.050). Participants who had higher adherence scores were discussing GFD with a specialist, obtaining educational materials, had enhanced symptoms associated with CD, and did not complain about the taste of GFD (p<0.050). Conclusion: Patients with CD has adequate knowledge of CD and adherence of GFD. No association was found between the knowledge of CD and GFD to the adherence of GFD. Further research might explore other potential factors influencing the adherence to GFD.