Research on attitudes toward immigrants and refugees largely focuses on intergroup conflict and related threats imposed by outgroup members. This study shifts the analytic focus to intragroup conflict: a domestic struggle among natives over how to handle recently arrived refugees and on their perception of foreign workers in general and Muslims in particular. By exploiting an exogenous variation in the interview timing of a nationally representative survey conducted in South Korea, a “new immigration destination,” this study offers a causal estimate (local average treatment effect) of domestic societal conflict on outgroup attitudes. Results from regression discontinuity (RD) analysis show that in its aftermath—immediately following the completion of a controversial e-petition sponsored by the anti-refugee group demanding that the government extradite asylum seekers—the public opinion of Korean adults toward foreign workers and Muslims became more, not less, favorable. Heterogeneous treatment effects are also found across two respondent-level characteristics: cosmopolitan identity and relative deprivation. Specifically, the focal relationship is more pronounced among individuals who identify less with cosmopolitan citizenship and among those who are more relatively deprived.