Illegal waste dumping has become a threat to human health and the global environment. In Hong Kong, the government has proposed a quantity-based municipal solid waste charging scheme to reduce waste. However, individuals may still dispose of waste improperly, even if such a scheme has been implemented. In this study, the neutralization theory was adopted and an online survey with 273 respondents was conducted to examine the reasons for improper dumping intentions. A principal component analysis identified two types of neutralization: intrinsic neutralization (including denial of responsibility, denial of injury, and defense of necessity) and extrinsic neutralization (including condemnation of the condemners and appeal to higher loyalties). A regression analysis showed that intrinsic neutralization and gender were significant factors for illegal waste dumping intentions when attitude toward illegal waste dumping was controlled.