Background: In intensive care units (ICUs), patients cannot sleep well. Aromatherapy is used for depression, anxiety, relaxation and disorders related with sleep and stress.

Aim: This study aimed to investigate the effect of lavender essential oil on the sleep quality and anxiety level of patients in coronary ICU.

Participants: A total of 60 patients in coronary ICU participated in this study.

Design: A randomized controlled study was conducted with 60 patients in a province located in the southeast of Turkey.

Methods: After informing the patients in both groups about the study, they were administered a questionnaire, Pittsburgh Sleep Quality Index (PSQI) and the Beck Anxiety Inventory (BAI) scale. The patients in the intervention group were given 2% lavender essential oil via inhalation for 15 days after which they were administered the same scales again to evaluate the sleep quality and anxiety. As for the control group, they were administered the same scales again after 15 days without the inhalation of lavender essential oil.

Results: Comparison of the PSQI and BAI scores of the patients in the control and intervention groups before and after the intervention showed statistically significant differences in the change in favour of the intervention group (p < 0·05).

Conclusion: Lavender essential oil increased quality of sleep and reduced level of anxiety in patients with coronary artery disease.

Relevance to clinical practice: As a non-invasive, cheap, easily applicable, cost-effective, independent nursing intervention and appropriate for cardiac patients, lavender essential oil could be applied in ICUs.