They said soldiers firing into the air retreated in trucks as the rebels late Wednesday moved into the town about 186 miles (300 kilometers) west of Abidjan, Ivory Coast's largest city. A San Pedro businessman and a hotel owner spoke on condition of anonymity for fear of reprisals.
The victory came the same day rebels seized the capital, Yamoussoukro.
San Pedro is Ivory Coast's second-largest port and the major export point for cocoa. Ivory Coast is the world's largest cocoa producer.
Incumbent Laurent Gbagbo refuses to accept defeat and hand power to Alassane Ouattara, who was declared the winner of November presidential elections.