The psychological health of children is a global health concern. The international Health Behavior in School-Aged Children (HBSC) study has surveyed the psychological health of youths in over 40 countries. The HBSC questionnaire includes a brief symptom checklist of psychological complaints, but it has not yet been validated. This study evaluated the construct validity of the psychological health self-report tool used in the HBSC study. We used data from 26,078 participants in the 2010 Canadian HBSC survey. The core HBSC questionnaire measured common psychosomatic complaints using the HBSC symptom checklist (HBSC-SCL). The Canadian survey included an additional series of questions that measure four dimensions of mental health (emotional problems, emotional well-being, behavioral problems, prosocial behavior). We used these items to evaluate the construct validity of psychological symptoms in the HBSC-SCL. We assessed internal construct validity using Cronbach's alpha and external construct validity using factor analysis and structural equation modelling. Factor analysis showed that the HBSC-SCL measures two factors, psychological and somatic complaints. Psychological complaints included feeling low/depressed, irritable/bad tempered, nervous, and difficulties sleeping. Internal validity of the psychological subscale was good (alpha=0.78). This 4-item subscale demonstrated convergent validity with indicators for emotional problems (correlation (r)=-0.79, p<0.001) and emotional well-being (r=0.48, p<0.001), and discriminant validity with indicators for behavioral problems (r=-0.17, p<0.001) and prosocial behavior (r=0.02, p<0.001). Results support the HBSC-SCL psychological subscale as a valid measure of psychological health in school-aged children. Future research is recommended to replicate findings in other youth populations.