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Introduction: Olfactory dysfunction (OD) is a well know symptom of coronavirus disease 2019 (COVID-19), accounting for 48 to 85% of patients. In 1 to 10% of cases, patients develop a chronic olfactory dysfunction (COD), lasting more than 6 months. Recently, platelet-rich plasma (PRP) was used in patients with non-COVID-19 COD and authors reported encouraging results., Methods: In the present study, we investigated the usefulness and safety of PRP injection in 56 patients with COVID-19 COD by the Sniffing Stick test (TDI score) and a linker-scale from 0 (none) to 3 (strong) and we compare the result to a control group., Results: At 1 month post-PRP injection, the mean TDI scores significantly improved by 6.7 points in the PRP group (p < 0,001), the mean self-assessment of improvement in smell function was 1.8 (mild-to-moderate) in the PRP group, which was significantly higher than the score (0.3) in the control group (p < 0,001)., Conclusion: Our results showed that PRP in the olfactory cleft can increase the olfactory threshold 1 month after the injection. Moreover, our results suggest that timing of treatment may be an important factor and that PRP is a safe treatment, because no adverse effects were reported throughout the study., Trial Registration Number: NCT05226546., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)