We monitored the response of endangered Lost River sucker (Deltistes luxatus) larvae and shortnose sucker (Chasmistes brevirostris) larvae prior to, and during the first 2 seasons after, restoration of historic wetlands at the mouth of the Williamson River, Upper Klamath Lake, Oregon. In 2006 and 2007 (prerestoration) and in 2009 and 2010 (postrestoration), we used pop nets set in shallow-water (<1-m-deep) wetland habitats to document the distribution and condition of larval fish throughout the Williamson River Delta Preserve, as well as at a reference site along the Goose Ray shoreline in Upper Klamath Lake. From prerestoration to postrestoration, we witnessed significant declines in abundance of larval suckers at the reference site along the Goose Ray shoreline but no similarly significant declines in the 2 pilot restoration projects (t = 9.92, df = 400, P < 0.0001; t = 0.8, df = 400, P = 0.3438). In 2009 and 2010, larvae were documented using the newly restored portions of the delta. Larval suckers captured during pre- and postrestoration in the pilot areas and during postrestoration in the restored areas of the preserve were more likely to have fuller guts than larvae captured at the reference site along the Goose Ray shoreline. Throughout the study, length trends were more variable than gut fullness trends: larvae captured in pilot areas prior to restoration were larger than those captured after restoration, and larvae captured at the reference site postrestoration were on average larger than postrestoration sucker larvae from the restored and pilot areas.