A portion of patients with oral lichen planus (OLP) may have nutritional deficiency. This study evaluated whether there was an intimate association of the deficiencies of hemoglobin (Hb), iron, vitamin B12, and folic acid and high blood homocysteine level with OLP. Methods: The blood Hb, iron, vitamin B12, folic acid, and homocysteine concentrations in 352 OLP patients were measured and compared with the corresponding levels in 352 age- and sex-matched healthy control participants. Results: We found that 77 (21.9%) OLP patients, 48 (13.6%) OLP patients, 25 (7.1%) OLP patients, and one (0.3%) OLP patient had deficiencies of Hb (men < 13 g/dL, women < 12 g/dL), iron (< 60 μg/dL), vitamin B12 (< 200 pg/mL), and folic acid (< 4 ng/mL), respectively. Moreover, 52 (14.8%) OLP patients had abnormally high blood homocysteine level. OLP patients had a significantly higher frequency of Hb, iron, or vitamin B12 deficiency and of abnormally elevated blood homocysteine level than healthy control participants (all p < 0.001). Upon further dividing OLP patients into those with major erosive OLP (MjEOLP; n = 67), minor erosive OLP (n = 202), and nonerosive OLP (NEOLP; n = 83), we found that MjEOLP patients had a significantly higher mean homocysteine level than NEOLP patients (p = 0.035). Conclusion: We conclude that there is a significant association of deficiencies of Hb, iron, folic acid, and vitamin B12 and abnormally high blood homocysteine level with OLP. There may be a close relation of high blood homocysteine level to severity of OLP.