Economic ideas have long shed light on diverse spheres of social and cultural life. Religion is no exception and has spawned a large and thriving subfield. However, whereas recent decades have famously witnessed a ‘behavioural’ turn in economics – with Nobel prizes going to two pioneers of the field, Daniel Kahneman in 2002 and Richard Thaler in 2017 – there has yet to be significant work done in the ‘behavioural economics of religion’. This is a shame; there are good reasons for thinking that behavioural-economic theories and findings might be particularly well suited to illumine several areas of practical church life. In what is hopefully a light and quasi-entertaining way, this article offers (wildly speculative!) applications of behavioural economic ideas to three live topics within the sociology of religion and/or pastoral theology: the ‘empty’ church, the success of US megachurches, and church planting.