While the acceptance of homosexuality has risen across many Western countries, we know little about whether or why attitudes have changed in the rest of the world. Here I investigate these questions while also testing the relative utility of three theories of what drives worldwide attitudinal change: (1) the postmaterialist thesis, which casts existential security as a main determinant; (2) world society theory, which emphasizes the influence of a diffusing global culture; and (3) multiple modernities theory, which points to the effect of region-specific cultural programs. Drawing on data from the integrated World Values Survey/European Values Survey (1981-2012), I use a longitudinal multilevel design to model worldwide change in the societal acceptance of homosexuality. In line with world society theory, the results show a broad worldwide upswing in the acceptance of homosexuality, driven largely by the diffusion of favorable global cultural messages. The results provide strong evidence that global culture has shaped collective attitudes globally, although the impact here is found to be less in more religious societies. At the same time, the analysis finds a widening attitudinal gap between countries, and, consistent with multiple modernities theory, suggests this is due in part to the role of region-specific cultural programs. Contrary to the postmaterialist thesis, existential security is not found to have influenced attitudes.