The theft occurred around 1 a.m. at the tavern at 1310 Drury Street in Center City.
Owner Christopher Mullins said they had dozens of outdoor reservations for Valentine's Day weekend, which were now in jeopardy.
"This time of year, it's a lot of money when we're not doing as much business," said Mullins.
The staff needs to keep their outdoor dining area warm since it's a busy weekend for them.
"We have a good track record on love," said Mullins.
McGillin's is a popular place for couples to meet for the first time.
The tavern staff has books that document all the married couples they helped kickstart.