Italy is a case study in lowest‐low fertility. Its internal heterogeneity is substantial and changing over time. The paper has two main aims. First, it aims at investigating whether the theoretical framework offered by the diffusionist perspective to fertility transition could still be relevant in explaining fertility changes in contemporary advanced societies. Second, the paper aims at investigating if and how the associations between fertility and a series of indicators of secularisation, female occupation, contribution of fertility of immigrants, and economic development change across space and over time. We make use of geographically weighted regressions and spatial panel regressions to model explicitly spatial dependence in fertility among Italian provinces over the period between 1999 and 2010. Results show that spatial dependence in provincial fertility persists even after controlling for standard correlates of fertility, consistently with a diffusionist perspective. Further, the local association between fertility and its correlates is not homogeneous across provinces. The strength and in some cases also the direction of such associations vary spatially, suggesting that the determinants of low fertility change across space. Finally, the associations between fertility and its correlates change over time. Copyright © 2015 John Wiley & Sons, Ltd.