The insufficiency of waste treatment capacity is a considerable challenge that must be solved by cultivating concern for waste problems. Correspondingly, this research investigated waste separation behavior (WSB) in rural Vietnam, specifically among 298 rural and semi-rural households, which were divided into livestock and non-livestock groups on the basis of livelihood. The study's objectives were to identify differences in WSB and waste separation performance between these groups using an independent samples t-test and to introduce new WSB-related constructs associated with the theory of planned behavior (TPB). The constructs, namely, awareness, perception, and socioeconomic factors (the ownership of a garden, the number of pigs and chickens raised, and the money saved from using waste), were incorporated into multiple regression models of the household groups. Results showed that the livestock group exhibits more positive attitudes toward waste separation, greater concern for subjective norms, a stronger awareness of the negative effects of waste, a more well-developed perception of the encouragement of waste separation, and higher waste separation performance than does the non-livestock group (p < 0.01). The multiple regression analyses indicated that the presence of a garden—a feature characteristic of rural areas in Vietnam—is a very significant and powerful factor that affects the locals' waste separation habits (p < 0.01). This finding is attributed to the fact that gardens are convenient places for disposing of waste. Another determinant of waste separation performance in the entire community is trust in the waste management capabilities and policies of local authorities. In the livestock group, all the proposed socioeconomic factors are significantly correlated with WSB (p < 0.01). In particular, households engaged in small-scale livestock farming present potential to initiate waste separation given the tendency of families who rear a few chickens to use waste as animal feed (β = −0.157, p < 0.01). Win–win outcomes are achieved by the livestock group when they segregate waste and use it as livestock feed. Finally, the newly introduced TPB constructs effectively represent WSB in the chosen context.