Despite economic transformations and urbanization, declining shares of the workforce employed in the agricultural sector, production costs in the agricultural sector and food prices remain high in Nigeria relative to those in some of the other developing countries. Understanding how the adoption of mechanical technologies is related to agricultural productivity is therefore important for countries like Nigeria. Using farm household data from northern Nigeria as well as various spatial agroclimatic data, this study shows that the adoption of key mechanical technologies in Nigerian agriculture (animal traction, tractors, or both) has been high in areas that are more agroclimatically similar to the locations of agricultural research and development (R&D) stations, and this effect is heterogeneous, being particularly strong among relatively larger farms. Furthermore, such effects are likely to have been driven by the rise in returns on scale in the underlying production function caused by the adoption of these mechanical technologies. Agricultural mechanization, represented here as the switch from manual labor to animal traction and tractors, has been not only raising the average return on scale but also potentially magnifying the effects of productivity-enhancing public-sector R&D on spatial variations in agricultural productivity in countries like Nigeria. Acknowledgement : This work was undertaken as part of and funded by the CGIAR Research Program on Policies, Institutions, and Markets (PIM), which is led by the International Food Policy Research Institute (IFPRI) and funded by CGIAR Fund donors, the United States Agency for International Development Food Security Policy project, the Syngenta Foundation, and IFPRI s Nigeria Strategy Support Program. This paper has not undergone IFPRI s standard peer-review process. The opinions expressed here belong to the authors and do not necessarily reflect those of PIM, IFPRI, or CGIAR. The authors are solely responsible for all remaining errors.