Objective: To compare the effectiveness of aromatherapy with lavender essential oil (EO) versus an EO synergy on psycho-emotional symptoms and fatigue of nursing professionals in the COVID-19 setting. Materials and Methods: This is a quasi-experimental pilot study conducted in 2020. The professionals were randomized in Group 1 — lavender, and in Group 2 — lavender and other EOs synergy. The instruments were validated in Brazil, namely the Self-Reporting Questionnaire (SRQ-20) and the Fatigue Pictogram, which were applied at three moments: before the intervention, after 21 days of intervention, and three weeks after the end of the intervention follow-up. The data were evaluated using Pearson’s x2 test or Fisher’s exact test (dichotomous variables) and Student’s t-test or Mann-Whitney test (continuous variables). Results: A total of 18 professionals participated, and both groups presented improved SRQ-20 scores (p < 0.010), which was maintained in the follow-up for Group 1 compared to the pre-intervention moment (p = 0.033). There was a significant decrease in fatigue in professionals in both groups (p = 0.010), but no difference was observed in the improvement of the impact of fatigue on daily life. Conclusions: There was a reduction in psycho-emotional symptoms and fatigue in nursing professionals who used aromatherapy during the COVID-19 pandemic in both groups.