Hydrokinetic turbines are an industry with growing interest. With many varying designs being put forward it is important to assess in depth the effects such technologies are likely to have on the local environment. In this study, the response of two downstream migrating juvenile salmonid species (brown trout and Atlantic salmon) to a three-bladed vertical axis hydrokinetic turbine was assessed in an experimental setup. A large, flow-controlled tank was used for 15 minute individual trials, in which 80 individuals were tested (40 of each species). Four water velocity settings (0 m/s – 0.4 m/s) were assessed during the study with 10 replicates for each treatment. No direct collisions were observed. Behavioural responses to the turbine were analysed in terms of pass events and active avoidance. It was found that trout were less likely to pass the turbine than salmon. In the case of both species fish preferentially passed around the turbine rather than passing through the turbine structure. This could have implications for turbine placement.