We investigated the impacts of urbanization on reproductive success of House Wrens (Troglodytes aedon). We compared reproductive effort and success for 33 nesting attempts in suburban sites (2.5–10 buildings/ha) and 43 nesting attempts in rural sites (<2.5 buildings/ha) in and around the Washington, D.C.– Baltimore, Maryland, metropolitan area. There were no differences in clutch initiation dates or clutch sizes between suburban and rural nests. However, nestlings at suburban nests weighed less and had smaller body size prior to fledging compared to nestlings at rural nests. Parental feeding rates differed between suburban and rural nests during the “early nestling stage” (day 3 to day 6), but not in the “late nestling stage” (day 8 to day 12) suggesting average quality of prey for nestlings may be lower at suburban sites. Overall, suburban nests fledged more young than rural nests largely because of higher rates of nest predation on rural nests. Further research on how food availability and predation affects nesting success of House Wrens and other birds along urbanization gradients may provide important insights into impacts of urbanization on birds.