This study is the first to explore the twin influences of online propaganda and news media on Islamists. We conducted 44 in-depth interviews with cognitively and behaviorally radicalized Islamist prisoners in Austria as well as former Islamists in Germany and Austria. We found that online propaganda and news media had interdependent influences on Islamists’ rejections of non-Muslims and Western politics, as well as on their willingness to use violence and commit suicide. Cognitively radicalized individuals were influenced by propaganda that blamed non-Muslims for opposing Islam; this was reinforced by online mainstream news reports of right-wing populism and extremism that propagandists selectively distributed via social media. Among behaviorally radicalized individuals, exposure to propaganda and news reports depicting Muslim war victims contributed to the radicalized individuals’ willingness to use violence. Moreover, propaganda and media reports that extensively personalized perpetrators of violence strengthened radicalized individuals’ motivations to imitate the use of violence.