Due to the increasing waste generation over the years in China, there is an urgent need to addressing this major problem by implementing effective household waste separation programs. Although past studies have tried to explain the waste behaviour from social and psychological motivations, there is little understanding as to the impact of individual moral obligation and past experience on forming waste separating intention. The aim of this study is to investigate key determinants influencing household waste separation intention and behaviour. Based on the theory of planned behaviour (TPB) model, we designed a survey questionnaire by taking account of determinants including residents’ attitude, subjective norm, perceived behavioural control, moral obligation, past behaviour, and demographic factors, with the prediction of household waste separation behaviour in mind. After obtaining 628 valid questionnaires from households in the city of Hangzhou, the partial least squares structural equation modelling (PLS-SEM) was conducted to evaluate the effectiveness of each construct. The results indicate that subjective norms, perceived behavioural control, past behaviour and intention significantly predict household waste separation behaviour, with past behaviour being the most significant construct to predict individuals’ intention and behaviour. Additional analysis on the moderating effect of different kinds of people in terms of their genders, ages, income levels and perceived policy effectiveness, to further evoke household waste separation behaviours is also discussed. The findings suggest insightful future policies that can focus on residents’ habit formation by providing the convenient location of waste separation and collection facilities, encouraging market-driven recycling programs and traders, promoting community campaigns and education which help residents to form favourable habits for protecting the environment.