A new gene encoding a Δ12 fatty acid desaturase-related protein was cloned from a multicellular basidiomycete Coprinus cinereus TD#822-2. The 1326bp full-length gene, designated as Cop-odeA, codes for a putative protein of 442 amino acids with a MW of 49224. The Cop-odeA yeast transformant accumulated four new fatty acids identified as 9,12-hexadecadienoic acid, 9,12,15-hexadecatrienoic acid, linoleic acid, and α-linolenic acid, which comprised 8.8%, 1.0%, 29.0%, and 0.6% of the total fatty acids, respectively. The Cop-odeA protein was confirmed to be a novel bifunctional fatty acid desaturase with both high Δ12 desaturase activity and unusual Δ15 desaturase activity.