John Ledyard has made fundamental contributions to game theory and its applications to economics and political science. His research on the theoretical foundations and applications of mechanism design has contributed greatly to our understanding of the roles of incentives and information in organizations, markets, and political systems. Ledyard was also the first to apply Bayesian games to political science, and he developed a general equilibrium approach to the theory of electoral competition and voting with private information. He has also worked actively in the practical application of the principles of economics and game theory, mechanism design, and market design to solve real-world allocation problems. These applications include the design of markets for trading pollution rights, combinatorial auctions, and portfolio trading in thin markets.

Ledyard was previously on the faculty at Northwestern University from 1970 to 1985 and at Carnegie Mellon University from 1967 to 1970. He was a Sherman Fairchild Distinguished Scholar at Caltech in 1977–1978 and a visiting professor at Caltech in 1983–1984. He received an honorary degree from Purdue University and Indiana University in 1993. He was elected an Economic Theory Fellow by the Society for the Advancement of Economic Theory (2011) and a fellow of the American Academy of Arts and Sciences (1999), the Econometric Society (1977), and the Public Choice Society (2004). He was the president of the Public Choice Society and has served on several editorial boards of economic and public choice journals, as well as on advisory committees to the National Science Foundation and other organizations.