Multibrooded species that undertake more than one nesting attempt per breeding season and individuals that breed over multiple years (breeding seasons) must decide whether to return to (or remain at) their former breeding site and social mate (fidelity) or to relocate (dispersal). During three breeding seasons (1998–2000), we examined breeding-site (territory and nest) fidelity and social-mate fidelity of Eastern Phoebes (Sayornis phoebe) (n = 435 adults captured and color-banded, n = 198 males, n = 237 females) both within years and between years. We also examined the influence of sex and previous reproductive success on breeding-site and social-mate fidelity decisions. Field research was conducted at Crane Naval Surface Warfare Center, Martin County, Indiana. Breeding-site (territory and nest) and social-mate fidelity were extremely high both within and between years. Only 23 instances of breeding dispersal to new territories were documented. Within years, Eastern Phoebe adults rarely dispersed to new territories; but after an initial nest failure, they were more likely to change nests within a territory for their second breeding attempt. Males were more likely to change territories between years; however, the distance dispersed between territories did not differ between sexes. Within-year social-mate fidelity was nearly universal with 85.5% of all males and 92.7% of females mating with the same mate during multiple breeding attempts. Divorce was uncommon and mate replacement usually occurred following mate disappearance and probable death. Within years, 2.4% of females and 4.8% of males divorced and paired with new mates for their next breeding attempt. Between-year divorce rates were low; of those birds for which the original mate was known to be alive, only 3.0% of females and 4.3% of males changed mates. The probability of divorce was not influenced by sex or previous reproductive success.