Thirty-seven products were labelled to indicate embodied carbon emissions, and sales were recorded over a 3-month period. Green (below average), yellow (near average), and black (above average) footprints indicated carbon emissions embodied in groceries. The overall change in purchasing pattern was small, with black-labelled sales decreasing 6% and green-labelled sales increasing 4% after labelling. However, when green-labelled products were also the cheapest, the shift was more substantial, with a 20% switch from black- to green-label sales. These findings illustrate the potential for labelling to stimulate reductions in carbon emissions.