Misinformation often continues to influence people's reasoning even after it has been corrected. Therefore, an important aim of applied cognition research is to identify effective measures to counter misinformation. One frequently recommended but hitherto insufficiently tested strategy is source discreditation, that is, attacking the credibility of a misinformation source. In two experiments, we tested whether immediate source discreditation could reduce people's subsequent reliance on fictional event-related misinformation. In Experiment 1, the discreditation targeted a person source of misinformation, pointing to a conflict of interest. This intervention was compared with a commonly employed message-focused correction and a combination of correction and discreditation. The discreditation alone was effective, but less effective than a correction, with the combination of both most effective. Experiment 2 compared discreditations that targeted a person versus a media source of misinformation, pointing either to a conflict of interest or a poor track record of communication. Discreditations were effective for both types of sources, although track-record discreditations were less effective when the misinformation source was a media outlet compared to a person. Results demonstrate that continued influence of misinformation is shaped by social as well as cognitive factors and that source discreditation is a broadly applicable misinformation countermeasure.