Holmes, 33, went dining with her six-year-old daughter Suri Cruise at a restaurant named Mr Chow Tribeca in New York when she saw a group of people wearing them, reported Daily Mail online.
The T-shirts belonged to the time when Holmes married in 2006 actor ex-husband Tom Cruise, urging the former to end the marriage.
The group hid the slogans when they came face to face with the actress.
"When they sat down, they exchanged an awkward glance with Katie, but she kept her cool and didn't say anything. The embarrassed Halloween crew quickly covered up the costumes before Suri got a chance to take a look," a source said.