Police directed traffic around Custom House Quay while the incident was ongoing.
A spokesman for Dorset Police said: “We were called to a road traffic collision at the Alexandra Gardens end of Weymouth Esplanade at 3.24pm.
The boy suffered only minor injuries, although he was taken by ambulance to Dorset County Hospital as a precaution.
The pavement was also cordoned off on the corner of St Alban Street near the entrance to Alexandra Gardens.
“A little boy was taken to Dorset County Hospital but suffered only minor injuries.”