The textile sector stands as a cornerstone of Bangladesh's economy, contributing significantly to the nation's export revenue, accounting for approximately 83.4% of the total. Within the textile industry, several processes necessitate substantial water usage, which often leads to heavy reliance on groundwater due to its accessibility. However, this dependence on groundwater poses a looming threat to the availability of safe drinking water for the local community. Narayanganj, located southeast of the capital, Dhaka, hosts many textile factories. The extensive exploitation of groundwater resources has precipitated a swift decline in the groundwater table, diminishing at an average rate of 1-2 meters annually. This study's core objective is to investigate the viability of utilizing rainwater as an alternative water source for textile wet processes in Narayanganj, where the yearly average precipitation amounts to 2,047 mm. The rainwater complies with the required physicochemical standards for use in textile wet processing. This research places its focus on integrating rainwater alongside groundwater for wet processing in the textile industry, thereby contributing to the realization of Sustainable Development Goals (SDGs) 6, 9, and 12. Cotton fabrics underwent dyeing and washing procedures using harvested rainwater, after which the samples underwent evaluation through tests for colour fastness during washing and rubbing (under both dry and wet conditions). The obtained results, falling within the 4-5 Grade range, unequivocally affirm the viability and efficiency of rainwater harvesting as a water resource for textile wet processing. This approach possesses the potential to meet a significant portion, ranging from 40% to 60%, of the water demands within the textile industry. The adoption of this alternative water source will alleviate the strain on groundwater reserves, presenting a sustainable solution to address the pressing concerns related to groundwater aquifer depletion. These findings are anticipated to deliver advantages to the Greater Dhaka residents, as well as relevant water management authorities, while concurrently fostering a positive impact on the environment.