Phenotypic plasticity is wide-spread in animals, but how plastic responses to predation threat affect traits under sexual selection and influence mating preferences is not well understood. Here, we examined how chronic predation risk during development and acute predation risk during mate choice affect the expression of male secondary sexual traits and female mating preference in the three-spined stickleback, Gasterosteus aculeatus. Males reared under chronic predation risk developed less intense red breeding colouration but showed higher courtship activity than males that grew up in a predator-free environment. Acute predation risk during mate choice did not influence male behaviour or ornamentation. Predation risk experienced during development did not affect female mating preferences, while acute predator presence induced a switch in preferences for male courtship activity. Male body size and eye colouration influenced the intensity of female mating preferences, while the trait changing most in response to predation risk during development (red colouration) had no significant impact. The observed interplay between developmental plasticity in male ornamental traits and environment-dependent female mating preferences may lead to dynamic processes altering the strength and direction of sexual selection depending on both the chronic and acute risk of predation. These processes may contribute to the maintenance of within- and among-population variation in secondary sexual traits, and may, ultimately, facilitate speciation.