When paper is stored for a period of time, yellowing and deterioration may occur. This can pose a significant problem for paper that requires long time storage. Optical Brightening Agent is typically added to printing paper which requires high brightness, but since it is a fluorescent dye, its lightfastness is poor. The goal of this research was to investigate the long-term effects of Optical Brightening Agent on optical property of paper. To shorten the time, the long-term effects were studied by accelerated aging using heat, light and UV. Types and optimum amount of Optical Brightening Agents were selected, then mixed with pulp slurry to form handsheets. The sheets were then subjected to accelerated heat aging at 105ºC for 0, 3, 6, 9, and 12 days, accelerated light aging using Xenon lamp for 0, 25, 50, 75, and 100 hours, and accelerated UV aging for 0, 25, 50, 75, and 100 hours. It was found that heat aging decreased the 420-550 nm reflectance of all samples, while light and UV aging decreased the 420-550 nm reflectance of only the sheets with Optical Brightening Agent. The results also indicated that accelerated aging might cause Optical Brightening Agent to degrade, and in some cases might cause other reactions to occur which accelerated paper yellowing to proceed faster than in the paper without Optical Brightening Agent. Heat aging seemed to cause changes in paper itself more than light or UV aging, while light and UV aging had greater effect on Optical Brightening Agent contained in the sheet, as confirmed by HPLC analysis.