Objectives: This study examined the relationship between knowledge of, and adherence to, the gluten-free diet (GFD) in a local population of adolescents with celiac disease (CD). The secondary objectives were to identify information sources used to learn about the GFD and to compare adolescents’ and parents’ knowledge of the GFD. Methods: Adolescents (12–17 years) with CD and their parents from pediatric gastroenterology clinics in Calgary, Alberta, completed an online survey containing a knowledge assessment (Gluten-Free Diet Quiz [GFD-Q]), an adherence scale, questions about GFD information sources, and demographic/clinical information. GFD-Q scores were deemed “sufficient knowledge” with correct identification of 3/3 gluten-containing foods, ≥4/7 gluten-free foods, and ≥ 4/7 foods that may contain gluten; otherwise, scores were termed “insufficient knowledge”. Results: Of the 40 adolescent-parent pairs, 15 of 40 adolescents (37%) had sufficient knowledge, and 25 of 40 adolescents (63%) had insufficient knowledge. Within the insufficient knowledge group, 14 of 25 (56%) did not correctly identify enough allowed gluten-free foods. Parents scored higher on the GFD-Q (67% had sufficient knowledge). Adolescents reported overall adherence to the GFD (88%), with adherence being similar between the sufficient and insufficient knowledge groups (80% versus 92%). The most helpful information sources included physicians, another person with CD, parent(s), and Google; apps were infrequently used. Conclusion: Adolescents report good adherence; however, they struggle with GFD knowledge, particularly in identifying gluten-free foods. Further research is required to explore GFD educational tools, including mobile apps and dietician-led teaching sessions.