The incident had occurred at around 2 am today (Feb. 25).
Police said three motorcycles, a car, and a three-wheeler were involved in the accident.
The injured, residents of Kumarakattuwa, were admitted to Chilaw Hospital and one of them was transferred to Colombo National Hospital, as his condition became serious.
The injured were returning home after a musical show in Eliwitiya.
Two women were among the injured.