Purpose: To assess the test–retest reliability of the EQ-5D-5L and the reworded Quality of Life After Traumatic Brain Injury Overall Scale (QOLIBRI-OS) for the general population of Italy, the Netherlands, and the United Kingdom (UK). Methods: The sample contains 1864 members of the general population (aged 18–75 years) of Italy, the Netherlands, and the UK who completed a web-based questionnaire at two consecutive time points. The survey included items on gender, age, level of education, occupational status, household annual income, chronic health status, and the EQ-5D-5L and reworded QOLIBRI-OS instrument. Test–retest reliability of the EQ-5D-5L dimensions, EQ-5D-5L summary index, EQ VAS, reworded QOLIBRI-OS dimensions and reworded QOLIBRI-OS level sum score was examined by Gwet’s Agreement Coefficient (Gwet’s AC) and Intraclass Correlation Coefficient (ICC). Results: Gwet’s AC ranged from 0.64 to 0.97 for EQ-5D-5L dimensions. The ICC ranged from 0.73 to 0.84 for the EQ-5D-5L summary index and 0.61 to 0.68 for EQ VAS in the three countries. Gwet’s AC ranged from 0.35 to 0.55 for reworded QOLIBRI-OS dimensions in the three countries. The ICC ranged from 0.69 to 0.77 for reworded QOLIBRI-OS level sum score. Conclusion: Test–retest reliability of the EQ-5D-5L administered via a web-based questionnaire was substantial to almost perfect for the EQ-5D-5L dimensions, good for EQ-5D-5L summary index, and moderate for the EQ VAS. However, test–retest reliability was less satisfactory for the reworded QOLIBRI-OS. This indicates that the web-based EQ-5D-5L is a reliable instrument for the general population, but further research of the reworded QOLIBRI-OS is required.