Background: Nigella sativa Linn (Ranunculaceae) is popularly known as black cumin with a wide spectrum of pharmacological activities including anti-inflammatory, antibacterial, antifungal and antihelmenthic. The seeds are externally applied for eruptions of skin. The seeds are used traditionally for psoriasis tropicus with general pain and eruption of patches. Objective: The ethanolic extract of Nigella sativa seeds were evaluated for antipsoriatic activity. Materials and Methods: The screening of antipsoriatic activity of 95% of ethanolic extract of Nigella sativa seeds by using mouse tail model for psoriasis and in vitro antipsoriatic activity was carried out by SRB Assay using HaCaT human keratinocyte cell lines. Results: The ethanolic extract of Nigella sativa seeds extract produced a significant epidermal differentiation, from its degree of orthokeratosis (71.36±2.64) when compared to the negative control (17.30±4.09%). This was equivalent to the effect of the standard positive control, tazarotene (0.1%) gel, which showed a (90.03±2.00%) degree of orthokeratosis. The 95% ethanolic extract of Nigella sativa shown IC50 239 μg/ml, with good antiproliferant activity compared to Asiaticoside as positive control which showed potent activity with IC50 value of 20.13 μg/ml. Conclusion: The ethanolic extract of Nigella sativa seeds also showed increase in relative epidermal thickness when compared to control group by confirming its traditional use in psoriasis treatment.