This study examines the attitude change process based on the heuristic-systematic model (HSM) in persuasion among two individuals holding different opinions, as the simplest situation of multiple directions of persuasion by different sources. Participants with restricted or unrestricted cognitive resources were asked their attitudes after reading two different persuasive messages: one was a persuasion from in-group member with weak arguments and the other was from out-group member with strong arguments. Cognitive resources were manipulated with a dual task (Study 1) and time constraints (Study 2) to allow either heuristic or systematic processes to predominate. Both studies showed participants were more likely to form their attitudes in response to the persuasion from in-group member, which had positive heuristic cues, with weak arguments under a restricted condition than under an unrestricted condition. This provides evidence that the HSM can explain the attitude change process under multiple-source-and-direction persuasion.