Background: It has been reported that vitamin D deficiency may be associated with the development of oral lichen planus (OLP). Given the high prevalence of vitamin D deficiency in many countries, we sought to determine whether it constitutes a comorbidity of OLP. Methods: One hundred and twenty patients clinically and histologically diagnosed with OLP were evaluated for their serum vitamin D levels. The results were compared to results from a control series of the same number of subjects matched for age and sex. Results: Vitamin D deficiency was diagnosed in 45% (n = 54) of OLP patients and in 26.7% (n = 32) of the control group. Vitamin D supplements were being taken by 32 (26.7%) OLP patients and 15 (12.5%) subjects in the control group. A multivariate logistic regression model showed that OLP was associated with vitamin D deficiency [OR: 2.24 (1.28–3.98, p = 0.005)] and vitamin D supplementation [OR: 2.51 (1.25–5.22, p = 0.011)], even after controlling for confounding variables such as sex, age ≤60>, tobacco, and alcohol. Conclusion: The association between OLP patients and vitamin D deficiency or vitamin D supplementation suggests that further research might explore the benefits of vitamin D supplements in managing OLP patients.