When local anesthetics are used, the administration of dexmedetomidine (DEX) can prolong analgesic duration. However, the effect of caudal DEX on high volume/low concentration (HVLC) local anesthetics has not been studied. We investigated the analgesic effect of DEX added to a HVLC of ropivacaine for caudal block in children. Eighty children (the American Society of Anesthesiologists (ASA) status I; age, 1–6 years) undergoing ambulatory orchiopexy were enrolled in the study. Children were randomly assigned to undergo a caudal block with 1.5 mL/kg of 0.15% ropivacaine and either 1 µg/kg of DEX (DEX group, n =40) or the same amount of saline (Control group, n =40) under general anesthesia. The results showed that the time to first analgesic request was significantly longer in the DEX group than in the control group. The sevoflurane requirement for anesthesia and frequency of emergence agitation (EA) were also significantly lower in the DEX group. There was no difference in adverse events between the two groups. In conclusion, a dose of 1 µg/kg of caudal DEX prolonged the first analgesic request time, although the immediate postoperative pain scores were comparable in both groups. Furthermore, caudal DEX significantly reduced the sevoflurane requirement and the frequency of EA.