Abstract One key trade-off underlying life-history evolution is the one between age and size at maturity, with earlier maturation leading to greater chances of juvenile survival at the cost of reduced fecundity as an adult. Here we model the impact of limited dispersal and kin competition on the stable resolution of this trade-off. We show that if mating is at least occasionally nonlocal, then limited dispersal favors juvenile survival over adult fecundity in females, promoting earlier female maturation at the population level; at the same time, it favors adult fecundity over juvenile survival in males, promoting later male maturation. Limited dispersal and local competition can thus drive the evolution of sexual dimorphism in the timing of maturation and consequent dimorphism in body size. At the individual level, if maturation can be flexibly adjusted in response to dispersal status, then both males and females who disperse as offspring should mature earlier than those who remain on their natal patch.