Headache is one of the most common symptoms following traumatic brain injury. In a prospective study of 212 patients with mild traumatic brain injury, 91% reported headaches within one year of injury. According to the International Classification of Headache Disorders, post-traumatic headache is defined as a headache that occurs within 7 days after one of the following: 1. head injury; 2. regaining consciousness after a head injury; 3. headache caused by withdrawal of medication after a head injury. Persistent post-traumatic headache refers to headache secondary to mild traumatic brain injury with symptoms persisting for more than three months. It has been reported in the literature that the prevalence of persistent post-traumatic headache after mild traumatic brain injury ranges from 47-95%. There are no FDA-approved medications for the treatment of persistent post-traumatic headache, and the exact mechanism is currently unknown. Given the long-term safety data for behavioral therapies, researchers have investigated the use of behavioral therapies for patients with persistent posttraumatic headache. Most prior behavioral studies have involved multimodal interventions, limiting the ability to assess individual nonpharmacological interventions. Progressive muscle relaxation has Grade A evidence for the prevention of migraine and tension headache. However, research on this behavioral therapy for persistent posttraumatic headache is very limited. One study reported using a smartphone app with a headache diary and progressive muscle relaxation audio files, instructing participants to record headache symptoms and practice 20 minutes of progressive muscle relaxation daily, followed by three monthly follow-up assessments. The conclusions suggest that progressive muscle relaxation provided by smartphones is feasible and may be a promising option for the treatment of patients with persistent posttraumatic headache. This is particularly useful for patients who are limited by cost, personal time, and provider availability. Future studies will require a larger sample size of patients with persistent posttraumatic headache to assess efficacy.