The requirements of higher cement content and numerous admixtures in self-compacting concrete (SCC) yield a comparatively high production due to the high cement consumption that limits its use in everyday construction. As a result, it is prudent to consider alternatives for decreasing the environmental effects while producing a cost-effective SCC. Therefore, this study aims to investigate the fresh mechanical, durability, and microstructural characteristics as well as the environmental impacts of self-compacting concrete (SCC) incorporating waste banana leaf ash (BLA) to determine the optimum percentage of BLA. Concrete mixtures with 10%, 20%, and 30% OPC substitutions were investigated. Test findings revealed that all the fresh mixes performed within the EFNARC (2002) recommended limit. Despite the fact that increasing concentrations of BLA reduced the mechanical properties, concentrations of up to 20% BLA demonstrated strength comparable to the control mix. Furthermore, chloride ion penetration increased to 4%, with 20% BLA replacement falling into the moderate ion permeability zone. Finally, a relatively lower CO2-eq (maximum 29.13% reduction) per MPa indicates a significant positive impact due to the reduced Global Warming Potential (GWP).