Both urbanization and a high share of youth (“youth bulge”) have been shown to correlate with higher levels of political violence, in general, and terrorism, in particular. In this article, we test the hypothesis that urbanization and general youth bulge (share of aged 15–29 in the adult population) should produce a particularly significant impact on the level of terrorist activity when acting together due to the interaction effect. Performed negative binomial regressions (both with and without interaction term) support this hypothesis. We also test the impact of “urban youth bulge” (share of urban youth in the total adult population), and it turns out to be a much more significant predictor of terrorism than either general youth bulge or urbanization taken separately. This finding is shown to have substantial practical implications, indicating that urban youth bulges are likely to retain their relevance in the forthcoming decades, in contrast to general youth bulges.