In the context of the popular development of the low-carbon economy, the “high energy consumption, high pollution, and high emissions” of the manufacturing industry have resulted in unprecedented difficulties in the development of this industry. To achieve nationally determined contribution targets, China has formulated a series of low carbon development plans for heavy industry to reduce carbon emissions. Among these, low-carbon technological innovation has been used a new means for manufacturing enterprises to achieve sustainable development, which is highly valued by management practice. Taking Chinese manufacturing companies as an example, the present study investigates the mediating effect of green core competence on the relationship between low-carbon technological innovation and enterprise performance and evaluates the moderating impact of firm size on this relationship. In this study, 438 valid data points were empirically analyzed, and the results indicate that low-carbon technological innovation significantly and positively affects enterprise performance of manufacturing. Green core competence plays a mediating role in the positive effect of low-carbon technological innovation on enterprise performance. Firm size has a positive moderating effect on the relationship between low-carbon technological innovation and enterprise performance. Meanwhile, firm size also moderates the relationship between low-carbon technological innovation and green core competence. Namely, a larger firm size correlates with a more positive effect on the cultivation of green core capabilities from the low-carbon technological innovation of manufacturing companies and in stronger enterprise performance. Finally, this work provides constructive guidance for Chinese manufacturing companies on how to practice low-carbon production and achieve sustainable development.