The rise of social impact accelerators (SIAs), such as climate and sustainability accelerators, has prompted inquiries about their value to social ventures – entrepreneurial endeavors that employ innovative business models and sustainable business practices to tackle societal grand challenges, such as climate change or systemic poverty. This study evaluates the role of SIAs in scaling social ventures using a large-scale database of 18,680 social ventures and their founding teams that applied to 404 accelerator programs, of which 43 percent had an explicit social impact focus. Using an inverse probability of treatment weights design, we find that accelerated social ventures in both generalist accelerators and SIAs scaled faster than similar non-accelerated ventures that applied to these programs. However, social ventures accelerated through SIAs scaled faster than those accelerated through generalist programs: they raised more philanthropic funding, were more likely to raise venture capital and raised more capital, had higher planned fundraising, and were more likely to scale their full-time employment. Social ventures accelerated through SIAs also experienced greater scaling of philanthropic funding and revenue when more peers in their cohort adopted formal impact evaluation metrics, such as GIIRS. These findings highlight the nuanced ways that SIAs support social venture scaling and development.