Psychopathology is defined in part by its impacts on life functioning (e.g., fulfillment of daily responsibilities at work or school, in family relationships). Relations to life functioning are particularly important in the validation of culture-specific syndromes (patterns of mental health symptoms specific to a particular culture), to demonstrate that culture-specific symptom patterns do in fact represent pathology. The current study's goal was to assess the construct validity of the Cambodian Somatic Symptom and Syndrome Inventory (CSSI). The study focused on the statistically unique effects of the CSSI on life functioning (i.e., effects of the CSSI on life functioning, controlling for Western psychopathology syndromes), to determine whether the CSSI contributes information beyond standard Western measures, which would support CSSI culture-specific convergent validity. Because adolescence is a key period when psychopathology often develops, study participants were 391 high-school students in one urban and one rural area of Cambodia. Participants completed the CSSI, the Western psychopathology surveys Patient Health Questionnaire (PHQ-9) and Generalized Anxiety Disorder questionnaire (GAD-7), and life functioning measures assessing functional impairment, quality of life, and help-seeking. Results indicated strong CSSI concurrent validity (canonical correlation = 0.75) with the PHQ-9 and GAD-7, and CSSI total effects convergent validity on life functioning indicators. All CSSI statistically unique effects (controlling for the PHQ-9 and GAD-7) on life functioning measures were non-significant indicating that the CSSI, shown to be a valid assessment measure in the current study, does not add predictive information beyond standard Western measures. A key limitation that should be considered in interpretation of these results is that the life functioning measures, although reviewed by Khmer psychologists, were Western-based, thus potentially inflating relations with Western psychopathology measures.