We compiled data to understand the organization of marine zooplankton based on their fundamental traits, such as body size or growth rate, rather than based on species names. Zooplankton, and in particular the dominant crustacean copepods, are central to marine food webs and the carbon cycle. The data include 14 traits and thousands of copepod species and may be used for comparisons between species or communities and ultimately to inspire better large-scale models of planktonic ecosystems.