The pink capri pants were found on the northern end of Good Harbor Beach in Gloucester by a person walking the beach on Friday, state police said.
The pants are consistent in size, color, and style with those that Caleigh Harrison was wearing when she disappeared while playing on Rockport's Long Beach on April 19, state police said.
The pants, found about a mile south of where the girl was last seen, were shown to members of the child's family, but they have not confirmed if they belonged to Caleigh, state police said.
"Obviously, they would love to be able to put this child to rest and this is the first break in the case," said Maureen Flatley, of the Mission for Missing Children. "I think there is the first possibility that they may be able to recover some remains, which is the best we can hope for."
After more than a week of water, air, and ground searches last spring, as well as an exhaustive missing person investigation by Rockport and State Police, investigators concluded that Caleigh Harrison likely somehow entered the ocean and was pulled out to sea.
No evidence connected to her disappearance was found at that time.