Workmen tackling a leak in the churchyard of St Mary's Church in Hinckley stumbled upon a burial chamber thought to be 100 years old.
The two Severn Trent workers were tackling the leak beneath a footpath in the graveyard.
Mark Kirk, of the digging team, said:
When we struck it the bricks fell away and we saw water in there, it was full to the top. We dropped our pump in and when I looked in there I saw a skull looking back at me.
The church now plans to reseal the chamber and decide whether Leicestershire Police need to be informed.