Culverts pose significant barriers to the upstream migration of small-bodied fishes, with high water velocities often impeding their movements. Installing baffles within culverts has been proposed as a solution to mitigate these effects. This rapid evidence synthesis reviews the effectiveness of various baffle designs for improving the abundance and diversity of small-bodied fish migrating upstream through culverts. The findings indicate that baffles generally enhance passage success compared to non-baffled culverts. However, simple passage efficiency metrics do not fully capture effectiveness. Emerging evidence suggests that turbulence within baffle arrays can significantly delay fish movements. Baffle designs that minimize large recirculation zones and maximize low-velocity zones, such as spoiler, vertical, and longitudinal baffles, are most effective. Conversely, weir-style baffles, which create large recirculation zones, are less suitable as they hinder and delay upstream movements. This synthesis highlights the importance of optimising baffle design to facilitate the successful migration of small-bodied fishes.