This study investigated the effects of imagining others on cooperation in a one-shot Prisoner’s Dilemma (PD) game. There are two ways to imagine others’ perspectives: “imagining the other” or considering how the other person feels, and “imagining the self” or projecting oneself onto the other person. Participants were assigned to one of three conditions: a) the imagining-other condition, b) the imagining-self condition, and c) the control condition (thinking about a landscape). Participants played a one-shot PD game and completed the social value orientation (SVO) scale, which measures one’s cooperative tendency. Results showed that the cooperation rate was higher in the imagining-other condition, and participants in the imagining-other condition expected that the partner would cooperate and that the partner thinks they would cooperate. In contrast, in the imagining-self condition, no significant differences were observed about these variables. Furthermore, the cooperation rate increased mediated by two-way expectations in the imagining-others condition, while it was not observed in imagining-self conditions. These results show the importance of imagining others not as a reflection of self, in increasing expectation of mutual cooperation and promoting cooperation.