This study aims to evaluate the potential of sugarcane bagasse ash (SCBA) as a supplementary cementitious material (SCM) in terms of composition. Using coal-combustion fly ash (CFA) as the benchmark, SCBA is characterized thoroughly using multiple tools to determine and compare particle size, particle morphology, chemical composition, glass content, element distribution and chemical status. It is found that SCBA has fine particle size (d50 = 6.76 μm, compared to 2.2 μm of CFA), high glass content (78.5 wt%, compared to 81 wt% of CFA), and relatively stable chemical composition, making it a potential effective SCM. The glass content of SCBA is dominated by amorphous silica (77.2%, compared to 53.6% of CFA), which can lead to formation of secondary calcium silicate hydrates in pozzolanic reactions. However, SCBA contains no spherical glass grains but many porous grains, which may compromise the workability of fresh-state cement-based materials. Another two detriments of SCBA are high carbon and potassium contents, which could potentially interfere the performance of cement-based materials. However, due to their existence forms (i.e., either light or dissolvable, as revealed by X-ray photoelectron spectroscopy), these detrimental effects can be mitigated through washing. A literature-survey based analysis shows that the ash samples adopted in this study are representative, so the conclusions drawn from this study are generally meaningful.