Background: Hand eczema severity index (HECSI) is a widely used tool for assessment of hand eczema (HE) severity. Generally, HECSI has been used by health care providers, and a validation of the HECSI tool when used by patients is lacking. Objectives: To evaluate the construct validity and reliability of HECSI as a tool for patients based on comparison to HECSI assessments by physicians. Methods: Patients with HE, enrolled from the dermatological outpatient clinic, Bispebjerg Hospital, assessed HE severity with a patient version of HECSI (patient-HECSI). Afterwards, HECSI was assessed by a trained physician (physician-HECSI). Results: This study found a strong correlation and very good absolute agreement between patient-HECSI and physician-HECSI assessments with a correlation coefficient of 0.756 and intraclass correlation coefficient (ICC) of 0.844. Cronbach's alpha was 0.861 indicating very good internal consistency. Conclusion: With a strong construct validity and reliability, the patient-HECSI may be used by patients as a patient-reported outcome assessing their personal HE severity.