A majority of consumers claim to prefer climate labelled food over non-labelled alternatives. However, there is limited empirical evidence that such labels actually influence consumer behaviour when shopping. In a randomized field experiment, conducted in 17 retrial stores in Sweden, the short run effects of a voluntary climate labelling scheme on milk demand were measured. Results suggest that climate labelling increased demand by approximately 7%. The response is significantly smaller than suggested by consumer surveys, but larger than observed in earlier studies of actual purchasing behavior where quantitative information on climate impact is provided.