Beef production contributes to environmental problems, such as climate change, air pollution and water pollution. Our objective was to determine how much the introduction of beef cow grazing on abandoned lands into a housing system (housed in barns throughout the year) alters environmental impacts. We used life cycle assessment to evaluate the environmental impacts of beef cow-calf systems with and without grazing on abandoned cultivated lands, on 11 Japanese farms. The functional unit was one marketed beef calf (Japanese Black) at 8 months of age. A reduction of global warming potential (GWP), acidification potential (AP) and eutrophication potential (EP) was found in all five grazing systems (including an experimental farm), compared with the average values for housing systems. A reduction of energy consumption was also found in the five grazing systems; however, the reduction was not large in one farm. Feed transportation and production were the main contributors to energy consumption, and unless there is a decrease in the energy consumption associated with these two processes, the energy consumption throughout the life cycle will not decrease. Thus, the introduction of grazing on abandoned lands can reduce environmental impacts, but the effects can be weakened or offset depending on the amount of imported feed. In the experimental farm with a grazing system, the reduction of GWP, AP, EP and energy consumption compared with the average values for the housing systems was 32, 48, 48 and 45%, respectively. In the four commercial farms with grazing systems, the reduction of GWP, AP, EP and energy consumption was 11-24, 13-22, 19-24 and 2-21%, respectively, which we regard as possible reductions in a real life situation. We conclude that a large reduction of environmental impacts could not be achieved solely through the introduction of grazing.