Paul McDonald, 44, was digging a swimming pool for his children when he struck a bone of the 10ft foot mammal with his digger.
The bottlenose dolphin is thought to have washed up on an ancient shoreline after the last Ice Age.
Archaeologists have described the prehistoric discovery in Causewayhead, Stirling, as "the find of a lifetime".
The father-of-four said he recognised the dolphin's skull by its long snout, rows of teeth and unmistakable shape.
The bones were preserved in clay, around 80cm below the current ground level, for what is thought to have been up to 8,000 years.
With them was a broken tool made from deer antler, which would have been used to carve the meat.
It is thought the dolphin was made into a meal by local hunter gatherers.
Mr McDonald, a medical rep in orthopaedics, who works with bones himself, said: "I was digging away in the swimming pool when I caught something unusual. I rolled it back and came down and pulled it out.
"I saw the roundness of the skull and then saw the snout and teeth and I knew right away it was a dolphin.
