This paper proposes a behavioral strategy called expectation of cooperation with which cooperation in the prisoner’s dilemma game spreads over agent networks by incorporating Q-learning. Recent advances in computer and communication technologies enable intelligent agents to operate in small and handy computers such asmobile PCs, tablet computers, and smart phones as delegates of their owners. Because the interaction of these agents is associated with social links in the real world, social behavior is to some degree required to avoid conflicts, competition, and unfairness that may lead to further inefficiency in the agent society. The proposed strategy is simple and easy to implement but nevertheless can spread over and maintain cooperation in agent networks under certain conditions. We conducted a number of experiments to clarify these conditions, and the results indicate that cooperation spread and wasmaintained with the proposed strategy in a variety of networks.