It happened around 6 p.m. Tuesday in Elizabethtown, Lancaster County.
Police said the 44-year-old man responded to an ad on Craigslist selling a television and met a young woman in a movie theater parking lot.
After asking if he had the cash for the TV, the woman began walking the victim toward a parked car when a man ambushed him and struck him in the head with the bat. The victim was struck two more times before gaining his feet and escaping.
Police said the victim was being treated at a hospital for head and arm injuries. Police didn't say if the victim was actually robbed.