ABSTRACT Extremist attacks pose a dangerous threat to society and past work suggests that many factors can contribute to radicalization. The present project aims to combine literature from multiple theories of radicalization to meta-analyze the association between basic psychological needs and extremism. From 46 articles containing 75 samples, 248 effect sizes were retrieved (N = 30,082). There is not a significant overall association between basic psychological needs and extremism. However, the operationalization of the need explains a significant amount of variance in the effect sizes, such that need satisfaction is negatively associated with extremism (r = −0.09, 95 percent CI [−0.15, −0.03]) whereas desire for a need is positively associated with extremism (r = 0.21, 95 percent CI [0.14, 0.28]). This finding suggests that how researchers define basic psychological needs is important when examining the role of needs in radicalization and theorists should continue to incorporate them in their models. Furthermore, the nature of extremism explains a significant amount of variance in the effect sizes, such that basic psychological needs are positively associated with Islamist extremism and negatively associated with far-left extremism. Directions for future research and implications for countering violent extremism interventions are discussed.