Sungai Besar's population is estimated to be around 23,000 of which 43% are within 20 to 55 years old. From that total, around 63 percent are Malays, Chinese (33%) and Indian (3.5%).
Majority of its people are working as farmers and fisherman, as well as working in coconut and palm oil plantations. The town becomes the centre of administration for Sabak Bernam district as many government offices and local authority centre are located there.