The importance of sustainable innovation achievement propels firms to consider the economic, social, and environmental dimensions of sustainable development. However, it is important to clarify that not all innovations impact sustainable development. Regardless of the limited circumstances in small and medium-sized enterprises (SMEs), intrapreneurship, stakeholder integration, and absorptive capacity are firm-specific capabilities that could be explored as strategic intentions of management practices in the organization. This paper investigated the mediating role of process innovation in the relationship among the firm-specific capabilities of absorptive capacity, intrapreneurship, and stakeholder integration for sustainable innovation in SMEs. This empirical study examines the manufacturing sector of Indonesian SMEs with a sample size of 190 firms. The study found that practices of process innovation, as a mediator triggered by the firm-specific capabilities of absorptive capacity, intrapreneurship, and stakeholder integration affect sustainable innovation, although at low stages. Finally, implications for the theory and practice of attaining sustainable innovation in SMEs are drawn.