This paper reports the characterization of Sarawak Fly Ash. The main focus is to identify the mechanical properties of geopolymer using Sarawak Fly Ash. The studies show that Sarawak Fly Ash can be an attractive construction material with respect to the high compressive strength obtained from Unconfined Compression Test. A series of tests are performed in this research such as scanning electron microscope, compressive strength test, x-ray fluorescence and particle size distribution. The results obtained show that SFA is predominantly smaller than 40µm, the compressive strength of sample curing for 1 day and 7 days are 42MPa and 55MPa respectively. The morphology of the Sarawak Fly Ash has also been studied. The strength development in geopolymer using Sarawak Fly Ash was mainly influenced by its particle size.