Intensive agriculture and industrial development have damaged ecosystem balance in many parts of the world along with changes in the gaseous composition of the earth atmosphere, hydrology, and the global climate. Legumes are the gift of nature that might appear to safeguard the environment and ensure win–win benefits for society, economy, and environment. Legumes in association with bacteria can fix atmospheric di-nitrogen (N2) in root nodules. Globally, land-based biological nitrogen fixation (BNF) exceeds the amount of industrial nitrogen (N) production by 1.1 times. Such fixed N is partly utilized by the succeeding nonlegumes and thus N fertilizer can be reduced without sacrificing cereal yields. Growing legumes in rotation with cereals can increase soil carbon (C) sequestration by 9–45 Mg C ha–1, and reduce greenhouse gases emissions by 5–7 times compared to nonlegumes. Legumes need less N and can be grown under water deficit conditions. The rate of N could be reduced roughly by 200 kg N ha–1 for nonlegumes grown after grain legumes. Such savings of N from BNF could reduce carbon dioxide (CO2) emission by approximately 200 kg ha–1. Beyond BNF, mineralization of legume residues adds N and other nutrients to the soil and improves soil fertility. Legume plants can improve soil aggregates, increase soil water retention, and have a stronger adaptive capacity to adverse environments. Legumes can smartly mitigate the negative effects of climate change and acclimatize to a vulnerable environment. The inclusion of legumes in the cropping systems increases yields of both legumes and nonlegumes. Legume plants, therefore, should get priority to be included in all cropping systems, forestry, and aesthetics to get maximum social, economic, and environmental benefits. Realizing the importance of legumes, the chapter endeavored to fetch an overall scenario of climate change, multiple dimensions of climate-smart legume-based cropping systems, future research avenues, and policy implications.