What reason underpins why people say they prefer eco-labeled over conventional products during direct perceptual comparison? One possibility is that there is no difference in the perceptual experience of the products; the participants just say there is because they wish to gain other’s approval. In this paper, we tested this social desirability account of the eco-label effect by requesting participants to judge grapes that were in truth identical but labeled “eco-friendly” and “conventional” respectively. The eco-label effects were similar in magnitude for an impression management condition (participants were told that their responses were monitored) and a no-instructions control condition, but greater in a moral-instructions condition (the participants were told, amongst other things, that conventional agriculture is harmful). The experiment suggests that people do not say that they prefer eco-labeled products because they seek other’s approval. Social motives may underpin reasons to purchase “green” products at the grocery store, but social motives are not the direct cause of the eco-label effect on the perceptual experience of the products.