We analysed growth plasticity of two Daphnia pulex clones under low-phosphorus (LP) and high phosphorus (HP) conditions, in the presence of Chaoborus kairomones to examine how food quality (P-availability) might impact life-history responses and vulnerability to predation. Overall, clone 1 grew faster, and was larger at maturity. Under HP, both clones responded to kairomones by increasing growth, age and size at maturity, and decreasing fecundity. Under LP, both clones suffered reduced growth, and fecundity. However, the magnitude of response to kairomones depended on a clone by P-availability interaction. Chaoborus presented a 1 : 1 clonal mixture under HP or LP, consumed more individuals under LP. Moreover, fewer clone 1 individuals were consumed. Studying the effects of P-availability on life histories, and predator–prey interactions may help us understand the mechanisms generating and maintaining plasticity, as well as influencing genotypic diversity and microevolutionary processes in natural populations.