Waterfowl management is a major goal at the Delta National Wildlife Refuge, yet there is little information on mottled duck (Anas fulvigula) nesting on the Mississippi River Delta (MRD) in Louisiana to guide management decisions. In 1998 and 1999, we determined nest success and its relationship to sites and habitat types. Average Mayfield nest success for all locations and years was 20.0%. Nest success differed among sites in 1998 and among habitat types in 1999. Greatest nest success (56.7%) was on Mississippi River levee sites and lowest nest success (0.3%) was on canal banks. Most nest failure was attributed to female abandonment (33.1%) and nest depredation (27.7%). Habitats selected for nesting sites were not used in proportion to their availability, with grassland habitats being used more than expected and marsh and forested habitats being used less than expected. No nests were located on splays. Habitat loss and degradation of coastal marshes in the MRD probably has an adverse affect on mottled duck nesting. Identifying nest locations and habitat types may allow managers to protect existing mottled duck nesting habitats or create new nesting sites.