Exposure to stress during development (in the form of elevated glucocorticoid stress hormones or food restriction), has been associated with sustained phenotypic effects across taxonomic groups.  Although the phenotypic consequences of developmental stress have been well-studied, there are comparatively few studies that have examined the fitness consequences of developmental stress via changes in reproductive success.  Developmental stress decreases the quality of sexually selected traits (e.g. bird song), and therefore is thought to decrease reproductive success.  However, animals exposed to developmental stress may compensate for poor quality sexually selected traits as adults by pursuing alternative reproductive tactics.  Here, I examine the effects of developmental stress on adult male reproductive investment and success in the zebra finch (Taeniopygia guttata).  I tested the hypothesis that males exposed to developmental stress sire fewer offspring through extra-pair copulations (EPCs), but invest more in parental care.  To test this hypothesis, I fed nestlings corticosterone (CORT; the dominant avian glucocorticoid) during the nestling period and measured their adult reproductive success using common garden breeding experiments.  I found that nestlings reared by CORT-fed fathers received more parental care compared to nestlings reared by control fathers.  Consequently, males fed CORT during development reared nestlings in better condition compared to control males.  Contrary to the prediction that developmental stress decreases male reproductive success, I found that CORT-fed males also sired more offspring, and were less likely to rear non-genetic offspring compared to control males, and thus had greater overall reproductive success.  These data are the first to demonstrate that developmental stress can have a positive effect on fitness via changes in reproductive success and provide support for an adaptive role of developmental stress in shaping animal phenotype.