Three suspected people-traffickers were arrested, a statement from the National Migration Institute said.
It gave no details on the size of the secret underground passage.
Police acted on an anonymous tip about a possible kidnapping of migrants held in a residential area of Tijuana, which borders California.
Tunnels of varying degrees of size and sophistication have been found in Tijuana. Authorities say some were used to smuggle both people and illegal drugs into the United States.
It was 200 meters long and was equipped with electricity and ventilation, officials have said.