Carpal tunnel syndrome is characterised by compression of the median nerve. The mainstay of treatment is surgical decompression. This case report highlights the occurrence of a persistent median artery, which could complicate surgery. A 55-year-old woman underwent carpal tunnel decompression. An incidental finding of a large-calibre persistent median artery, which was superficial to the flexor sheath, could have been damaged. This was carefully retracted and the procedure was completed, without any complications. Several studies have shown the prevalence of persistent median artery to range from 1.1-27.1%. It is usually found deep to the flexor retinaculum but in this case it was found to be just beneath the palmar fascia. There is increased chance of iatrogenic injury with this particular variant. Surgeons performing the procedure should be mindful of this variation, because accidental damage could result in devastating consequences to the hand.