This study investigates the effect of fly ash in bamboo-reinforced mortar wall panels. The effect of fly ash with bamboo has been quantified by evaluating the material properties of bamboo, the compressive strength of mortar mixes, composite panel properties through non-destructive testing techniques and by evaluating the flexural strength of panels through two-point loading tests. Nine panels were fabricated with mortar mixes categorised into three groups based on mix proportion. Test results showed that bending cracks promote debonding of mortar layers under flexure with the addition of fly ash in wall panels due to lower bond strength development. Because of the reduced surface hardness and resilience, the first crack load and ultimate load were lowered compared to panels developed without fly ash. Debonding failure under flexure loads was observed, which leads to a reduction in flexural strength of the panels with the addition of fly ash, although significant compressive strength and cost-effectiveness was achieved.