A man has been seriously injured after falling from a yacht mast in Gisborne.

Around 3.40pm the 35-year-old fell 12 metres onto the deck of the yacht while it was berthed at a marina near the Tatapouri Sports Fishing Club.

St John Ambulance Communications shift manager Norm Ngatai says witnesses reported the man hit the mast's spreaders as he fell.

He says the man sustained major trauma in the fall and it's likely he'll be transferred to Waikato Hospital.