Predation risk and mate availability affect phenotypic expression in many taxa, yet their effects have heretofore been considered in isolation.  Since both predation risk and mate availability affect growth, the timing of sexual maturity, and the amount of resources allocated to reproduction, there are good reasons to consider them congruently.  We examined how predation risk and mate availability interact to affect morphology, life history, and reproduction over the entire lifespan of the simultaneously hermaphroditic freshwater snail Physa acuta.  Predator cues induced rapid juvenile growth, delayed reproduction, and investment in defense.  The presence of a sexual partner reduced allocation to growth with long-term consequences for longevity and fecundity.  In the absence of predator cues, snails without mates produced twice as many eggs as snails with mates; however, the pattern was reversed in the presence of predator cues.  Female reproductive investment did not change with mate availability or predation risk.  Therefore, increased investment in male function may explain the reduced growth and longevity of mated snails in the absence of predator cues.  Therefore, our results are indicative of a trade-off between growth, longevity, and the allocation of resources between male and female reproduction.  Consideration of this interaction is crucial in future studies of inducible defenses and mating-system plasticity.