This study compared immobilization of gemsbok (Oryx gazella) using thiafentanil-xylazine (TX) versus carfentanil-xylazine (CX). Twelve adult gemsboks were divided into two groups, TX and CX. Each group received either 6 mg thiafentanil (0.036 µg/kg (0.032–0.040 µg/kg) and 20 mg xylazine (TX) or 3.6 mg carfentanil (0.021 µg/kg (0.017–0.024 µg/kg) and 20 mg xylazine (CX). Once handled, physiologic measurements were taken every 5 min for 20 min. There were few physiologic differences between the groups, although TX gemsboks were more hypertensive. Quality of induction, quality of recovery, depth of anesthesia, and muscle relaxation were subjectively assessed. Although TX gemsboks showed a trend for more-rapid induction and recovery postantagonist administration, this difference was not statistically significant. Similarly, there was a trend for TX animals to have smoother inductions and improved immobilization quality, but only the quality of induction was significantly different. These trends suggest that TX is preferable to CX when anesthetizing adult gemsboks.