Constrained access to land is increasingly recognized as a problem impeding rural household welfare in densely populated areas of Africa. This study utilizes household and plot level data from rural Kenya to explore the linkage between land access and food security. We find that a 10% increase in operated land size would increase total cereal consumption and home produced food consumption by 0.8% and 2.0%, respectively. We also find that land rental is the dominant mechanism that poor rural farmers use to access additional land for cultivation. However, the levels of long-term land investment (measured by applications of organic manure) and land productivity are significantly lower for rented plots than for own plots even after household fixed-effect and plot level observed characteristics are controlled for. Furthermore, land rental markets do not allow farmers to fully adjust their operated land size to their optimal level. These findings point to the existence of problems with land rental markets that impede their ability to fully contribute to national food security and poverty reduction goals.