Concussion or mild traumatic brain injury (mTBI) is a major public health concern. Most adolescents will recover from mTBI without complication; however, a sizeable minority experience symptoms that last more than one most post-injury (i.e., persisting symptoms after concussion). Few evidence-based treatments exist for adolescents with persisting symptoms after concussion. Mindfulness-based interventions (MBIs) are effective for treating a wide range of mental and physical health conditions that overlap with post-concussion symptoms. Participants will participate in an 8-week smartphone app-based MBI or a health education program as a control. The study will determine the practicality of doing a larger study to evaluate the effectiveness of the MBI by assessing participants' level of interest, view of intervention helpfulness, and their completion of all the components of the study.