Raising public awareness of the Sustainable Development Goals (SDGs) is a critical prerequisite for their implementation. However, little is known about attitude formation among the public toward SDGs at the national level. We explored this topic in China, a country that has emerged as a leading world economy with strong transformational imperatives to work toward sustainable development. Following Chaiken’s heuristic–systematic model and using data from an online survey with 4128 valid respondents, this study investigated the factors that affect public support for SDGs and explains how individuals form supportive attitudes. Our empirical evidence showed that in China, first, public support is mainly shaped by demographic attributes (gender, age, and educational attainment), value predispositions (e.g., altruistic values and anthropocentric worldviews), and the level of SDG-relevant knowledge. Second, an interaction effect exists between value predispositions and knowledge among the public concerning support for SDGs. Third, the Chinese public views the implementation of SDGs as a part of development policy rather than environmental policy. This study provides empirical findings on the factors that account for public attitudes toward SDGs, outlining some useful implications for designing policy tools that would bolster SDG action.