<p>Temperature is one of the most important biological factors involved in ectotherm development, growth and reproduction. Temperature can have direct effects on phenotype, such as survival, development, or reproductive allocation. For example, parents may trade-off between producing fewer, larger eggs in cooler conditions, and more, smaller eggs in warm conditions. Additionally, temperature can also shape indirect (parental) effects in a process called transgenerational plasticity. However, the nature of temperature’s direct and indirect effects is poorly known in most species. In this study, we manipulated both parental and developmental thermal environment in a full-factorial, split-clutch design to investigate how thermal regime, both constant and diurnally fluctuating, impacts reproductive allocation and development of the freshwater snail <i>Physa acuta</i>, and if thermal regime has transgenerational effects. We found that temperature impacted life stages differently. Hot parental environments suppressed reproduction of parent snails, but hot developmental temperature accelerated development and growth of embryos compared with cooler developmental temperatures. We found no evidence that the thermal environment of parents affected any offspring trait, nor evidence of reproductive allocation strategies in response to temperature. These differential influences of ambient temperature on adult vs. juvenile life stages of <i>P. acuta</i> could have implications for population growth and survival under climate change.</p>