Aims: The aim of this study is to provide more information on the relation between the COVID-19 pandemic and externalizing problems in children and adolescents with mental health problems. In...Show moreAims: The aim of this study is to provide more information on the relation between the COVID-19 pandemic and externalizing problems in children and adolescents with mental health problems. In addition, this study examined the potential influence of gender and age on the relation between the COVID-19 pandemic and externalizing problems. Methods: This study is based on a between-subjects design that examined externalizing problems among children and adolescents between the ages of 8 and 18 years in a youth care sample (N = 3,215) before the COVID-19 pandemic (April 1, 2019–March 10, 2020, N = 1,873) and during the pandemic (March 11, 2020–April 1, 2021, N = 1,342). The Child Behavioral Checklist (CBCL) was used to measure externalizing problems. Parents or legal guardians filled in this questionnaire at the beginning of treatment. Results: No increases in externalizing problems were found in children and adolescents during the COVID-19 pandemic compared to children and adolescents before the pandemic. In addition, gender and age did not influence the relation between the COVID-19 pandemic and externalizing problems significantly. Conclusions: Our results are not in line with most previous research. However, they are in line with recent research that found initial increases in mental health problems at the start of the COVID-19 pandemic, but not over time. This research contributes to the knowledge and sheds new light on the impact of the COVID-19 pandemic on the mental health of children and adolescents referred to youth care.Show less