Sustainable consumption is increasingly promoted as a key response to environmental challenges, yet consumers’ pro-environmental intentions often fail to translate into actual purchasing behaviour. The primary objective of this study is to compare the relative influence of eco-labels and online product reviews on consumers’ green purchasing behaviour, conceptualising both information sources as cognitive heuristics in e-commerce decision-making. Using data from a cross-sectional online survey conducted in the Czech Republic (N = 1,028), the analysis explores the relationships between self-reported green purchasing habits, the perceived influence of eco-labels, and online review behaviour.