In this article, we present the findings of the first systematic scoping review of scientific literature on radicalization into violent extremism since the Al Qaeda attacks on 11 September 2001. We selected and categorized all scholarly, peer-reviewed, English-language articles published between 2001 and 2015 that empirically investigated the factors of radicalization into violent extremism (N = 148). In the analysis we consider two main dependent variables (behavioral and cognitive radicalization) and three main independent variables (push, pull, and personal factors). “Pull” factors of radicalization emerge as the main factors of radicalization across studies focused on different geographical areas and ideologies. This article points to the need to focus more on the interaction between push, pull, and personal factors, and to diversify the methodologies used in the field.