Online retailing can lower the environmental impact of shopping under specific circumstances. As a result of the numerous variables involved, most of the studies that have compared the carbon footprints of online and conventional retailing only take a partial view. To make a more holistic assessment, this study develops a framework that accounts for all the relevant environmental factors relating to retail/e-commerce activities. Variables related to consumer shopping behaviour such as basket size, transport mode, trip length and trip frequency are included in the analysis. This framework is used to build a Life Cycle Analysis model. The model is applied to different online retail methods for fast-moving consumer goods in the United Kingdom. We find that, within the “last mile” link to the home, the nature of the consumer's behaviour in terms of travel, choice of e-fulfilment method and basket size are critical factors in determining the environmental sustainability of e-commerce. The nature and routing of van deliveries, the amount and type of packaging used, and the energy efficiency of shop and e-fulfilment centre operations are also identified as significant contributors to climate change potential. The results of this study indicate ways in which e-commerce can be made more environmentally sustainable, encouraging consumers to reduce complementary shopping trips and maximise the number of items per delivery. This study identifies the strengths and weaknesses of a range of e-retail channels and provides a basis for future research on the environmental sustainability of online retailing of fast-moving consumer goods.