Previous research suggests that threat can bolster anti-immigration attitudes, but less is known about the effects of threat on ideological tolerance. We tested the hypothesis that realistic threats — tangible threats to e.g., the safety or financial well-being of one’s group — bolster support for right-wing extremists. In Experiment 1, participants (N = 200) learned that crime and unemployment rates were either increasing (high threat condition) or remaining the same (low threat condition). Consistent with our hypothesis, higher threat lead to a significant increase in tolerance for right-wing, but not left-wing, extremists. In a second, pre-registered extended replication experiment (N = 385), we added a baseline (no threat) condition. Additionally, attitudes to immigrants were examined as a mediator. This experiment produced non-significant threat effects on tolerance of right-wing extremists. Overall, the current research provides weak support for the hypothesis that realistic threats have asymmetric effects on tolerance of political extremists. However, consistent with previous research, people were more tolerant of extremists within their own ideological camp.