Between December 2002 and September 2017, 125 anesthetic procedures involving free-living and orphaned captive mountain gorillas (Gorilla beringei beringei) were performed in the Virunga Massif and Bwindi Impenetrable Forest in East-Central Africa. Of these 125 immobilizations, 114 records were complete enough for inclusion into this study. Anesthetic and physiologic data from these 114 cases were analyzed, of which 57 used medetomidine–ketamine and 57 used dexmedetomidine–ketamine administered intramuscularly. With the use of estimated weights, the mean induction dosage (mg/kg ± SD) for medetomidine was 0.033 ± 0.003 (n = 42), for dexmedetomidine 0.018 ± 0.005 (n = 53), and for ketamine 3.66 ± 0.95 (n = 95). Mean time from injection of induction dose to recumbency was 6.8 ± 3.1 min (n = 74). Atipamezole was administered intramuscularly to reverse anesthesia. First signs of recovery occurred at 5.0 ± 4.0 min, and full recovery was 19.0 ± 17.0 min after administration of the reversal agent. No significant differences in physiologic parameters or anesthetic time variables were noted between healthy and unhealthy individuals. Mean heart rate was 72.0 ± 17.6 beats/min (n = 83) and mean oxygen saturation was 96.5% ± 4.2 (n = 62). Mean respiratory rate was 27 ± 9 breaths/min (n = 84) and mean body temperature 36.6°C ± 1.2 (n = 61). The current protocol has several advantages for field use in this species given its quick induction, few observed side effects, and ability to reverse so that the animal can return more quickly to its social group.