Starch gelatinization behaviors significantly affect functionalities of starch-based foods and materials. Various analytical techniques have been used to measure starch gelatinization behaviors, but these instruments are not commonly found in laboratory and industrial settings. This study aimed to investigate whether spectrophotometer, a more ubiquitous instrument, could be used for measuring starch gelatinization. The relative crystallinity and enthalpy of starch granules remained unchanged during heating at 54–56 °C, but decreased at higher temperatures. The transmittance of starch slurry at 620 nm also remained unchanged at 54–56 °C, but significantly increased at higher temperatures. Furthermore, the changes in transmittance were negatively and significantly correlated with both the changes in relative crystallinity and enthalpy. This suggested that changes in transmittance of starch slurry during heating could be used to evaluate the temperature at which starch gelatinization occurred. However, further research is needed to determine if the changes in transmittance of starch slurry can be used to evaluate the thermostability of starch granules during heating. These findings offer a simple and feasible pathway for measuring starch gelatinization properties using ubiquitous spectrophotometer.