One of the major challenges of our present society is the protection of the environment. Some of the important elements in this respect are the reduction of the consumption of energy, natural raw materials and the utilisation of waste materials. The used of waste is showing prospective application in construction as alternative to conventional materials. It conserves natural resources and reduces the space required for the landfill disposal. Palm kernel shell is a byproduct of the production of palm oil. Previous works indicate that palm kernel shell performs satisfactorily as an aggregate for lightweight concrete. This research therefore was carried out in an attempt to evaluate the performance of sisal fiber in palm kernel shell concrete. The palm kernel shell used for this research was determined to have a specific gravity of 1.36, bulk density of 574 kg/m3 and was therefore classified as lightweight aggregate. Values of water absorption and porosity of the shell were found to be 11.43% and 14.70% respectively. A mix proportion of 1:2:4 and water-cement ratio of 0.63 was adopted for all the concrete mixes. A total 36 concrete cubes of size 150mm x 150mm x 150mm were cast with 1%, 2% and 3% sisal fiber and were crushed to obtain the compressive strength at 7, 14 and 28 days of curing, 12 concrete beams were also produced and tested for flexural strength. An increase in compressive strength by 51.2% was observed at 3%. It was concluded that 3% sisal fiber can be adopted for lightweight concrete work.