Rising costs and a growing sense of environmental consciousness are among the important factors that drive the search for alternative materials in concrete production. This study investigated the potential of Bamboo Stem Ash (BSA) as a supplementary cementitious material in concrete production. This was done by varying the percentage composition ratios of Bamboo Stem Ash to Ordinary Portland Cement (OPC) in both concrete and mortar at 5 : 95, 10 : 90, 15 : 85 , 20 : 80 , 25 : 75 and 30 : 70%. The concrete cubes were prepared using binder/sand/stone ratio of 1:2:4 and water/cement ratio of 0.6 while the mortar cubes were prepared using a binder/sand/water ratio of 1:3:0.5. Results from the study show that the best combination of the BSA to OPC ratio for optimum concrete strength is 10%: 90% for which the compressive strength at 28 days of curing was 22.88 N/mm 2 in comparison with 24.58 N/mm 2 obtained for the control sample. For mortars replaced with the varied percentages of BSA, a slow rate of strength gain was observed even after curing for 28 days.