Ripened coconut water is a by-product of food industry in Southeast Asia countries include Malaysia. It is usually drained as effluent from the coconut processing factory into the environment which might cause pollutions. The aim of this study is to investigate the suitability of underutilized ripened coconut water as low cost carbon source for curdlan production by Agrobacterium sp. ATCC31749. Besides, un-ripened coconut water was also used as carbon source in the fermentation medium of Agrobacterium sp. ATCC31749, instead of ripened coconut water, under similar fermentation conditions such initial pH and incubation times. Seed culture of Agrobacterium sp. ATCC31749 strain was initially grown in Luria-Bertani (LB) medium before been transferred into 2L flask containing the fermentation medium supplemented with coconut water. The incubation was conducted at 30 °C for seven days. Optical density (OD) measured by UV spectrophotometer showed that coconut waters as the carbon source supported the growth of Agrobacterium sp. ATCC 31749. Curdlan production by Agrobacterium sp. ATCC31749 was comparatively higher (10.831 mg/mL) with un-ripened coconut as the carbon source compared to ripened coconut water that yielded 9.546 mg/mL of curdlan. The result indicated that both un-ripened and ripened coconut water are suitable to be used as the carbon source for curdlan production by Agrobacterium sp. ATCC 31749.This study revealed how coconut water as the by-product waste in the food industry can be applied as substance for the production of value-added product.