Working memory, one of the cognitive components, may be impaired in patients with multiple sclerosis. Accordingly, this study aims to determine the effects of aromatherapy with lavender essential oil on the working memory of women with multiple sclerosis (MS). In this clinical trial, 60 women with multiple sclerosis were selected using the sampling method from patients referred to the MS Clinic of Rafsanjan. Based on the inclusion and exclusion criteria, the participants were randomly divided into intervention and placebo groups. In addition, the working memory test developed by Daneman and Carpenter was used to evaluate the participants’ working memory before the intervention and the day after the last intervention. The collected data were analyzed using SPSS Statistics version 18.0. According to intragroup comparison results and based on the paired t-test, the mean score of the working memory before the intervention in the intervention group was 82.77±6.87, which increased to 87.64±5.57 after the intervention (P<0.001). The average working memory score of the placebo group was 80.30±11.09 and 82.09±11.31 before and after the intervention, respectively, which did not have a statistically significant difference (P=0.154). Based on findings from the independent t-test, the mean scores of working memory had a statistically significant difference between the intervention and placebo groups after the intervention (P=0.02). According to the results from this study, aromatherapy with lavender essential oil improved working memory in women with multiple sclerosis.