Background: During the last decade, a lot of co-morbidities (diabetes, obesity, heart disease, etc.) have been described to be associated with psoriasis, but the exact link at the molecular level is not well-known. Researchers have shown molecular level changes in vitamin D pathway and its relationship to cathelicidin. Aims: To estimate the levels of cathelicidin (LL-37), and vitamin D in psoriasis patients with co-morbidities, and compare them with matched healthy controls. Methods: One hundred consecutive patients with stable plaque psoriasis (psoriasis area and severity index ≥10) with no systemic treatment in the past 3 months were investigated for the serum levels of vitamin D and LL-37, and compared with equal number of matched healthy volunteers. Results: The serum vitamin D levels were significantly lower in patients. Furthermore, the levels of serum LL-37were significantly high. Conclusion: Our study showed that the low serum levels of vitamin D, and higher blood levels of cathelicidin could form a molecular level clue in the pathogenesis of psoriasis patients, who are more likely to develop co-morbidities.