Renewable energy technology innovation (RETI) is a crucial way to improve energy poverty and combat climate change. However, few studies have examined the impact of RETI on industrial green transformation and upgrading (IGTU) from the perspective of spatial spillover and its regional boundary. Based on the theory of green growth and sustainable development, this paper expands the connotation boundary of IGTU and measures the IGTU levels of 30 provinces in China from 2006 to 2020 using an improved entropy weight method. Kernel density estimation and Moran’s I index are adopted to portray temporal and spatial patterns, the spatial Durbin model is employed to examine the influencing mechanism and spatial spillover effects of RETI on IGTU and its regional boundaries, and the differential impact of its spatial effects on time, region, resource endowment, and environmental regulation are explored further. The results show that (1) RETI and IGTU in China are steadily increasing, indicating a decreasing spatial differentiation pattern of “east–west”; (2) RETI significantly promotes local IGTU but inhibits neighboring IGTU, forming a “beggar-thy-neighbor” situation; (3) the spatial spillover effect of RETI on IGTU has significant regional boundaries—the spatial spillover effect significantly negative and persists up to 800 km, but it is significantly positive from 800 to 1400 km and shows a trend of increasing and then decreasing; and (4) the promoting effect of RETI on IGTU gradually increases over time, presenting spatial differences of promotion in the east and inhibition in the west. Furthermore, RETI has a more substantial promoting effect on IGTU in non-resource-based regions and strong environmental regulation regions. The findings for China provide concrete evidence for formulating targeted policies and seeking a path for IGTU for other developing countries.