Stress in children and adolescents is common and related to many developmental problems. However, most studies have made no distinction between temporary or chronic stress due to the lack of a suitable questionnaire. This study tested the factor structure, reliability and validity of the 17-item self-report Chronic Stress Questionnaire for Children and Adolescents (CSQ-CA) in three samples, that is, 717 adolescents from the general population, 161 adolescents of parents with a severe chronic medical condition (CMC) like multiple sclerosis, and 113 adolescents with healthy parents. Results showed that a one-factor solution provided a reasonable fit overall. Reliability was good (α = .80 to .88). Convergent validity was supported by positive relations between total stress scores and internalizing and externalizing problem behaviors, experience of daily hassles, and maladaptive emotion regulation strategies and negative relations with quality of life, happiness, mindfulness, self-esteem, and coping skills. Adolescents from all samples, who themselves had a light CMC like asthma, showed higher chronic stress levels than those without a CMC. In line, adolescents of parents with a severe CMC reported more chronic stress than those of healthy parents, and adolescents with a chronic illness themselves and a parent with a chronic illness, showed the highest scores across the two family types. Overall, this study presents Child Ind Res (2018)