Whether sexual selection can promote adaptation in variable environments is unclear. Sexual selection can promote adaptive evolution when adult sexual traits predict offspring fitness, but environmental variation is expected to break down associations between sexual traits and offspring fitness. If, however, adult sexual traits predict adaptive offspring plasticity, then sexual selection can promote adaptation in the face of environmental variation. Here, we present data demonstrating that mate preferences of female spadefoot toads (Spea multiplicata) predict offspring plasticity and fitness across natural populations. Specifically, in populations where more females prefer exaggerated forms of a condition-dependent male sexual signal, tadpoles are more likely to express an inducible resource-use phenotype and grow larger. We additionally present experimental evidence that condition-dependent male sexual signals covary with the expression of tadpole plasticity and tadpole fitness. Our findings provide evidence that plasticity can serve as an indirect benefit of mate choice in variable environments. Our data also suggest that mate preferences for traits indicative of offspring plasticity can maintain associations between sexual traits and offspring fitness, thereby highlighting how sexual selection and plasticity can interact to facilitate adaptation even in heterogeneous environments.