AbstractAimTo assess the immediate and late effects of the COVID‐19 pandemic on the oral health‐related quality of life (OHRQoL) of adolescents.DesignThis is a longitudinal study performed with adolescents (11–15 years old) from Southern Brazil who were evaluated before the COVID‐19 outbreak, and 3 (T2) and 15 (T3) months after the beginning of the pandemic. OHRQoL was assessed using the CPQ11‐14. Sociodemographic and clinical variables were also collected. Changes in OHRQoL before, 3 and 15 months after the start of the pandemic were analyzed through multilevel Poisson regression models for repeated measures.ResultsA total of 290 adolescents were evaluated at T1, 207 were re‐evaluated at T2, and 204 at T3. Overall CPQ11‐14 scores over follow‐ups were 11.0 (SD 8.0) at T1, 8.3 (SD 7.8) and 12.8 (SD 8.8) at T3. Compared to T1, adolescents presented 29% lower overall CPQ11‐14 scores (IRR 0.71 95% CI 0.66–0.75) at T2, and 11% higher scores at T3 (IRR 1.11 95% CI 1.05–1 0.17), especially for the emotional and social well‐being domains.ConclusionCOVID‐19 pandemic impacted the adolescents' OHRQoL differently over time, indicating a reduction in impacts immediately after the beginning and worsening over long term exposure to this scenario.