Ultraviolet radiation (UVR) has an overall negative effect on zooplankton. The direct effects (i.e., when the individual is exposed to UVR) include mortality due to DNA damage, and changes in feeding, reproduction and respiration. The effects can also be indirect, for example when UVR affects food quality of phytoplankton. However much of our knowledge comes from freshwater zooplankton (copepods but especially cladocerans), whereas marine studies are comparatively scarce. Here we summarize the current knowledge in marine copepods and try to give an overview of knowledge gaps and interesting areas for further research. The indirect effects of UVR are likely to be more important (and less predictable due to interactions with other factors across trophic levels) than the direct effects.