Development is essential to understanding organismal phenotypes, including adult traits relevant to fitness and health. We studied how social behavior develops in the highly social cichlid fish, Astatotilapia burtoni . Focal fish were studied as juveniles (2 months old), through reproductive maturation, until young adulthood (6 months old). For the first 2 months, fish were housed and observed in freely-interacting triads, then tested individually in a battery of four behavior assays: open field exploration, social cue investigation, dominance behavior, and subordinate behavior. Fish were then housed in groups of 6 fish for an additional 2 months, after which they were tested individually again using the same battery. Body size was measured throughout the experiment, and gonadosomatic index (GSI) was quantified at the end. We find that overall repeatability of behavior across the four time points was low. However, principal components analysis revealed that the variance structure of all behavior measures remained remarkably stable over time. These results suggest that behavioral phenotypes can vary considerably throughout early life, while at the same time, the overall parameter space any individual can traverse throughout behavioral development may be somewhat invariant. Finally, we investigated the development of traits relevant to adult reproductive success, such as body size, somatic growth, and GSI, using model selection and averaging. Both morphological and behavioral traits, especially submissions, are predictive of young adult phenotype. Together, our results expand our understanding of behavioral development and the origins of individual variation in adult phenotypes.