Abbey Hawkins, 19, of Norwich, was driving to work when she felt a slight vibration on her chest but thought it was just her vibrating mobile phone in her jacket pocket.
The hotel receptionist had been wearing the bra for five hours when she plucked up the courage to investigate and found a baby bat in padding in her 34FF bra.
"That shocked me very much at the time, but it scuttled off under the desk into the dark. I was shaking from head to toe.
It looked quite cosy and comfortable in there so it was quite rude of me to take it out.
I did not notice anything as I put my bra on. The night before I had had one or two drinks and I was getting ready quickly.
The bra was in my drawer but it had been on the washing line the day before."
The bat was captured by one of her colleagues and stomped on before it had the chance to drain their blood.