Suicide terrorism is one of the deadliest terrorist strategies adopted by various terrorist groups around the world, but the 9/11 terrorist attacks have made suicide terrorism a popular attack strategy among terrorist organizations at the global level. However, there is scarce research on the effect of the 9/11 attacks on suicide terrorism. Using data obtained from the Global Terrorism Database (GTD) between 1981 and 2018, this research examines the effect of the 9/11 terrorist attacks on suicide terrorism and different types of terrorist organizations that commit suicide terrorism before and after 9/11 and the changes in the trends in the outcomes. The results of negative binomial regression tests comparing pre-9/11 and post-9/11 and monthly interrupted time series analyses showed that the 9/11 terrorist attacks had significant impacts on the above-mentioned outcomes. The results suggested that the 9/11 attacks have played a critical role in inspiring and encouraging terrorist organizations – religious-based ones in particular – to adopt suicide terrorism as an attack strategy.