Nutrient abundance during development has profound effects on adult morphology, life history and behaviour in many insects, but effects of nutrition on juvenile development are less well known. We investigated how larval diet quality affects patterns of growth, development and survival of larvae and pupae in the neriid fly Telostylinus angusticollis (Enderlein). We reared flies on two larval diets varying in nutrient concentration (‘rich’ versus ‘poor’) that have been shown previously to affect a wide range of adult traits in this species. We found that nutrient concentration affected larval growth trajectories, with individuals reared on the rich diet exhibiting greatly accelerated growth and reaching a larger body size. By contrast, we found no evidence that diet affected timing of development at the pupal stage, suggesting that developmental constraints may prevent variation in pupal development rate. Although overall mortality during the immature stages was not affected by larval diet, we found some evidence that individuals reared on a poor diet might experience higher larval mortality, whereas individuals reared on a rich diet might experience higher mortality during emergence from the puparium. Our results enhance understanding of the effects of nutrition on growth, development, and life history.