Abstract Natural and sexual selection can be in conflict in driving the evolution of sexual ornamentation. Sexual selection favours detectability to potential mates, whereas natural selection penalises detectability to avoid predators. Focusing on signal efficiency rather than detectability, however, suggests that natural and sexual selection need not be antagonistic. Considerable evidence demonstrates that people prefer images that match the statistics of natural scenes, likely because they are efficiently processed by the brain. This “processing bias” suggests that background-matching camouflage can be favoured by natural and sexual selection. We conducted an online experiment and showed for the first time human preference for camouflaged stimuli. Because the underlying visual mechanisms are shared across vertebrates, our results suggest that camouflage patterns could serve as evolutionary precursors of sexual signals.