A developmental understanding of the expression of posttraumatic stress (PTS) symptoms following trauma in childhood requires identifying continuity and change in not just overall symptoms but in the individual symptoms as well. Such models of change also require understanding multiple dimensions of time. That is, longitudinal change-the passage of time-may have different effects on symptom expression depending on when in time an individual entered the study - such as what age they were when first assessed. This paper addresses these ideas with an overview of the developmental differences in the assessment of PTS from the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, (DSM-5), longitudinal research on posttraumatic stress disorder (PTSD) symptoms, and providing synthesis within a symptom network perspective. We then provide an illustration of how individual PTSD symptoms change over time at different ages (elementary versus middle school) with a secondary analysis of data from a previously reported study (n = 191 youth, aged 8-15, assessed at two time points six months apart). The reanalysis of the data suggests both continuity and change in symptoms over time (i.e., some symptoms were more stable than other symptoms) with differences in symptom rates and their longitudinal change as a function of age (i.e., some symptoms more common or more stable in younger versus older or older versus younger). We close with avenues for future research aimed at better understanding symptom cascades over time and at different ages and potential implications for future iterations of assessment/classification systems.