Objective <p>To investigate the effects of inhaled lavender and geranium essential oils on pain, sleep and physiological parameters in patients who underwent laparoscopic cholecystectomy.</p> Methods <p>This is a randomized controlled study with a single-blind parallel group. A total of 153 patients were assigned to 3 groups, including control, lavender, and geranium groups, with 51 patients in each group by a stratified block randomization method. Inhalation aromatherapy with lavender and geranium essential oil was administered to 2 intervention groups, respectively. Patients in the control group only recelved standard treatment. Physiological parameters, pain intensity, and sleep quality were recorded before surgery, the day of surgery, and one day after surgery.</p> Results <p>There was no significant difference in the pain intensity among 3 groups before aromatic oil inhalation (<i>P</i>&gt;0.05). A significant decrease in the pain intensity was observed in the patients with aroma inhalation after surgery compared with the control group (<i>P</i>&lt;0.01). A higher increase in sleep quality was observed in the geranium group compared with the lavender group (<i>P</i>&lt;0.01). There was a significant difference within the groups in terms of physiological parameters (<i>P</i>&lt;0.05). Moreover, a significant weak correlation was observed between the frequency of analgesic use and pain intensity on the first postoperative day in the lavender group (<i>r</i>=−0.297, <i>P</i>=0.034), and between the frequency of analgesic use and postoperative sleep quality in the geranium group (<i>r</i>=0.297, <i>P</i>=0.034).</p> Conclusion <p>Inhalation aromatherapy with lavender and geranium essential oils in patients who underwent laparoscopic cholecystectomy decreases pain intensity, increases sleep quality, and stabilizes physical parameters in the preoperative and postoperative periods. (Registration No. NCT05464602)</p>