A dishwasher appliance includes a mid-level spray arm assembly and a diverter disposed in a conduit of the assembly. The diverter includes a disk positioned within a chamber and rotatable about an axis, the disk defining an aperture for selectively controlling fluid flow from the chamber into outlet channels, the disk movable along the axial direction between a first position and a second position, the disk defining a channel and a plurality of cams projecting into the channel. The diverter further includes a biasing element configured to urge the disk into the first position, and a boss extending from the housing into the channel of the disk, the boss defining a plurality of guide elements. The guide elements and cams are configured to interact so that movement of the disk along the axial direction between the first position and the second position causes the disk to rotate about the axis.