The police received first reports of the incident around 7:45 a.m. (11:45 GMT), CNN reported. The shooting halted the parade, held as part of the city's annual Caribbean Carnival, Boston Police Commissioner Michael Cox was quoted by the broadcaster as saying.
The victims were taken to hospitals with non-life-threatening injuries, the report said. The police arrested two individuals and seized multiple firearms, media reported.
No other details were immediately provided.