Background: Celiac disease (CD) is an autoimmune condition triggered by gluten ingestion in genetically predisposed individuals. Management typically involves a strict gluten-free diet (GFD). However, there are limited data concerning adherence to GFD among adult CD patients in Saudi Arabia. Therefore, this study aimed to pilot test the assessment of knowledge, adherence to GFD, and barriers to adherence to GFD among adult celiac patients in Madinah, Saudi Arabia. Methods: Cross-sectional data were collected from 36 adults with celiac disease at King Fahad Hospital, Madinah (2021–2022). After obtaining consent, participants completed an online questionnaire covering sociodemographic data, GFD knowledge, adherence, and related barriers. Results: Only 33% of participants were aware of the Ministry of Health’s GFD support program, with 30.6% utilizing gluten-free products and 27.8% receiving financial assistance. Higher adherence scores were significantly associated with awareness of the program, reading nutrition labels, understanding GFD requirements, receiving financial support, and using separate utensils for gluten-free food preparation. The majority (58.3%) had not consulted a dietitian, and no significant association was found between dietitian consultation and GFD adherence. Poor knowledge and difficulty interpreting nutrition labels were reported as primary barriers. Conclusions: Improving public and patient awareness of the GFD and available support programs is essential in enhancing adherence among CD patients in Saudi Arabia. Healthcare providers should play a more active role in patient education and ongoing support.