The purpose of this study is to develop a better understanding of what makes consumers reduce waste in order to address climate change, particularly when dining out. To accomplish this goal, this research constructs an extended theory of planned behavior model, using four main constructs of attitude, subjective norm, perceived behavioral control, and behavioral intention and incorporating climate change awareness and mitigation pursuing actions, anticipated pride and guilt, and high and low levels of dining expenses. An online survey was conducted of 482 respondents aged 20 years old or over who had dined in restaurants in the previous month in 2019. A partial least squares-structural (PLS) equation modeling analysis has been utilized with multi-group analysis. Results reveal that climate change awareness has significant effects on attitude and behavior intention, and climate change mitigation pursuing actions positively influence attitude and behavioral intention to reduce waste. Consumers' anticipated emotions lead to their behavioral intention. Diners' behavioral intention to reduce waste is significantly influenced by their attitude, subjective norms, and perceived behavioral control on waste reduction in restaurants. The levels of dining expenses significantly moderate seven out of nine hypotheses. Research on consumers' waste reduction in relation to climate change is not sufficiently conducted in the foodservice sector. Using an extended theory of planned behavior (TPB) to understand diner behavior related to waste reduction and climate change, this study therefore makes an important contribution to improving sustainability in foodservices, especially in the Asian context.