Oclacitinib is a selective Janus kinase (JAK) inhibitor that targets cytokine signaling involved in pruritus and inflammation. Oclacitinib is currently used to treat canine atopic dermatitis. In addition to its anti-pruritic action, recent finding suggests that oclacitinib inhibits the response of the transient receptor potential vanilloid type 1 (TRPV1) agonist capsaicin. In this study, we assessed the effect of oclacitinib on anesthesia-induced hypothermia and postoperative inflammatory pain in mice. Male ICR mice were used in the present study. Oclacitinib (10/45 mg/kg) or vehicle was orally administered to the mice, and the core body temperature was measured under inhalant isoflurane anesthesia. Subsequently, laparotomy was performed on each mouse, and postoperative pain was assessed using the Mouse Grimace Scale (MGS) and von Frey filament test. Serum interleukin-6 (IL-6) level was measured using ELISA. Oclacitinib administration did not influence core body temperature during isoflurane anesthesia. Results of both MGS and von Frey filament test showed that oclacitinib inhibited postoperative pain in a dose-dependent manner. Mice treated with oclacitinib exhibited a decreasing trend in serum IL-6 levels compared to those treated with the vehicle. In conclusion, JAK inhibitor oclacitinib showed analgesic action in a mice-laparotomy model, suggesting its potential as an analgesic agent for the management of postoperative pain.