The integration of manufacturing and services is a key factor driving the development of the manufacturing sector. Thus, this study uses Chinese province–industry data to determine the effect of such integration on resource allocation and manufacturing labor productivity. Additionally, heterogeneity is systematically examined, while avenues for its improvement are explored. Based on the results, dividing integration into forward and backward integration shows that both types significantly enhance manufacturing labor productivity by improving resource allocation efficiency, with forward integration demonstrating a more pronounced effect. This mechanism mainly manifests in capital- and technology-intensive industries but not in labor-intensive ones. Notably, while the integration of manufacturing and services enhances both economic and social efficiency by curbing capital over-allocation, it creates the problem of labor over-allocation. These conclusions provide value insights for promoting industrial transformation and upgrading.