Although sex differences in anxiety sensitivity or the specific tendency to fear anxiety-related sensations have been reported in adults with clinical pain, there is a dearth of relevant research among children. This study examined sex differences in anxiety sensitivity across unselected samples of 187 children with chronic pain (71.7% girls; mean age = 14.5) and 202 non-clinical children (52% girls; mean age = 13.6). Girls in the chronic pain and non-clinical samples reported elevated anxiety sensitivity relative to boys irrespective of clinical status. Girls with chronic pain also reported heightened fears of the physical consequences of anxiety compared to non-clinical girls but there were no such differences for psychological or social concerns. Among boys, anxiety sensitivity did not differ between the chronic pain and non-clinical groups. Future longitudinal research may examine whether specific fears of anxiety-related somatic sensations constitutes a sex-based vulnerability factor in the development of chronic pain.