We assessed wetland fish assemblage structure before and after restoration (hydrological reconnection, habitat improvement, and sediment manipulation) of an off-channel, riverine wetland. We selected three sites at the restored wetland (impact group) associated with the Lower Muskegon River, and three sites at nearby Muskegon Lake (control group). The Muskegon River flows into Muskegon Lake, which is connected to Lake Michigan, USA. We hypothesized that restoring lateral connectivity of the riverine wetland would result in: (1) a more diverse fish assemblage more similar to Muskegon Lake, and (2) improved water quality. Sites were sampled once before (2018) and three times after (2022 and twice during 2024) restoration. We used triplicate fyke nets to sample fishes and measured a suite of physicochemical variables. Across all years, dominant fishes captured included Largemouth Bass (Micropterus nigricans), Round Goby (Neogobius melanostomus), and Pumpkinseed (Lepomis gibbosus). Nonmetric multidimensional scaling indicated that temporal variability was minimal at control sites and that species composition at impact sites became more similar to control sites post restoration. At impact sites, species diversity, evenness, and richness increased post restoration. Pairwise comparisons of dissolved oxygen and specific conductivity showed significant differences between control and impact sites prior to restoration, yet no significant differences after restoration. Turbidity was consistently higher at impact sites, and coverage of submerged aquatic vegetation showed strong seasonal variability but increased substantially post restoration at impact sites. Thus, we found evidence that restoring lateral connectivity resulted in a more diverse fish assemblage that was more similar to control sites and improved water quality, which supported our initial hypotheses.