Background: Stress is a condition that occurs when the physical and psychological borders of the organism are threatened. If stress is experienced continuously and intensively for a long time, it causes anxiety. Nursing is one of the professions which experiences intensive stress. In particular, increasing the quality of nursing care in intensive care units is directly related with decreasing nurses’ stress and anxiety levels. Aims: This study aims to investigate the effects of aromatherapy on the stress and anxiety levels of nurses working in intensive care units. Methodology: The study is self-controlled and quasi experimental clinical study in nature. Sample of the study was 45 nurses working in the intensive care units which were surgical intensive care unit, coronary intensive care unit, neurology intensive care unit, cardiovascular surgery intensive care unit, medical intensive care unit, brain surgery intensive care unit and pediatric intensive care unit in two hospitals. The data were collected through the Personal Information Questionnaire developed by the researcher, Perceived Stress Scale, State-Trait Anxiety Inventory and Visual Analog Scale. Arterial blood pressure and pulse of nurses were measured before and after the application, and all the data were recorded. Statistical analysis was performed using SPSS 20.0 for Windows. Results: The lavender applied to nurses was found to have no effects on stress and anxiety levels or vital signs (p>0.05). However there was a significant decrease in the nurses’ state anxiety scores before and after the application in the experimental and control groups (experimental group p<0.001, control group p<0.001). Conclusions: Aromatherapy did not have any effects on nurses’ anxiety levels, but the 10 or 15 minutes breaks they spent in a quiet, lighted, and spacious room had positive effects, and thus decreased their state anxiety scores.