Stress increases the risk of road accidents by impairing driving performance. Although lavender is known for its calming effects, it remains unclear whether its use can reduce both cognitive (self-reported) and physiological stress in driving situations. In a simulated driving scenario, participants were randomly assigned to an experimental group exposed to lavender or to a control group. Physiological responses were measured via skin conductance response (SCR) and heart rate (HR), while on subjective level the NASA-TLX and a single-item self-report measure were attached. Contrary to expectations, lavender exposure generally elevated both physiological and self-reported stress levels. However, conscious perception of the scent moderated this effect, with participants who were aware of the lavender reporting significantly lower subjective stress. These findings suggest that the effectiveness of lavender depends on cognitive awareness, offering novel insights into olfactory interventions in high-stress environments.