Eucalyptus oil has been reported effective in reducing pain, swelling, and inflammation. This study aimed to investigate the effects of eucalyptus oil inhalation on pain and inflammatory responses after total knee replacement (TKR) surgery. Participants were randomized 1 : 1 to intervention group (eucalyptus inhalation group) or control group (almond oil inhalation group). Patients inhaled eucalyptus or almond oil for 30 min of continuous passive motion (CPM) on 3 consecutive days. Pain on a visual analog scale (VAS), blood pressure, heart rate, C-reactive protein (CRP) concentration, and white blood cell (WBC) count were measured before and after inhalation. Pain VAS on all three days (P < .001) and systolic (P < .05) and diastolic (P = .03) blood pressure on the second day were significantly lower in the group inhaling eucalyptus than that inhaling almond oil. Heart rate, CRP, and WBC, however, did not differ significantly in the two groups. In conclusion, inhalation of eucalyptus oil was effective in decreasing patient's pain and blood pressure following TKR, suggesting that eucalyptus oil inhalation may be a nursing intervention for the relief of pain after TKR.