Introduction Many studies have suggested a link between vitamin D deficiency and the development of other atopic diseases like allergic rhinitis (AR). AR can lead to sleep disturbance, fatigue, depressed mood, and compromised cognitive function, which can impair the quality of life and productivity in many people. Objective We aimed to determine the association between vitamin D levels and AR and the effect of vitamin D on atopy markers. Methods All patients with AR who were diagnosed, treated, and followed up at the King Abdulaziz University Hospital (KAUH), Jeddah, Saudi Arabia from January 2012 to January 2020 were included in the study. Our exclusion criteria were as follows: pediatric patients, patients with insufficient follow-up data, patients with no atopy markers, patients with comorbid conditions affecting their serum vitamin D levels, and patients with a history of taking medications that affect serum vitamin D levels. Results Fifty-five adult patients with AR were included in the study. Patients with vitamin D deficiency were more likely to have uncontrolled AR. Regarding the effect of vitamin D deficiency on atopy markers, there was no statistically significant relationship between vitamin D deficiency and serum immunoglobulin E (IgE) levels. However, serum eosinophil levels were significantly higher in patients with vitamin D deficiency. Conclusion Our results showed that vitamin D deficiency is strongly associated with uncontrolled AR; there was a statistically significant relationship between vitamin D deficiency and eosinophil levels, but no significant relationship between vitamin D deficiency and serum IgE was found.