Measures of body dysmorphic disorder symptoms have received little psychometric evaluation in adolescent samples. This study aimed to examine cross-sex measurement invariance in the Body Image Questionnaire–Child and Adolescent version (BIQ-C) to establish whether observed sex differences in total scores may be meaningful or due to differences in measurement properties. A sample of 3,057 Australian high school students completed the initial screening item of the measure (63.2% male, M_age = 14.58 years, SD = 1.37, range = 12-18 years). Of these participants, 1,512 (49.5%) reported appearance concerns and thus completed the full measure. Partial scalar measurement invariance was established among a revised two-factor, 9-item version of the BIQ-C (BIQ-C-9). Females reported significantly greater latent factor variance, higher BIQ-C-9 total and factor scores, and higher scores on most individual BIQ-C-9 items. The measure can be used with caution to compare body dysmorphic disorder symptoms between male and female adolescents, though sex-specific cutoff scores should be used.