With the number of threatened species increasing globally, conservation breeding is vitally important now more than ever. However, no previous peer-reviewed study has attempted to determine how the varying conditions across zoos have influenced breeding by an extinct-in-the-wild species. We therefore use questionnaires and studbook data to evaluate the influence of husbandry practices and enclosure design on scimitar-horned oryx (Oryx dammah) breeding success, at the herd level. Regression models were used to identify the variables that best predicted breeding success among 29 zoos across a five-year period. Calf survival decreased with herd age and the use of soft substrates in hardstand areas (yard area usually adjacent to the indoor housing), explaining 30.7% of overall variation. Calf survival also decreased where herds were small and where food provisions were not raised (and hence likely incited competition), although these were less influential. Likewise, birth rate decreased with soft substrates in hardstand areas and unraised food provisions, although these were less influential than for calf survival. Birth rate increased with year-round male presence, yet this decreased calf survival. Compared to previous studies, the number of enclosure/husbandry influences on breeding were relatively few. Nevertheless, these few enclosure/husbandry influences explained over one third of the variation in calf survival. Our data therefore suggest some potential improvements and hence that extinct-in-the-wild species stand a greater chance of survival with empirical design of zoo enclosures and husbandry methods.