New daily persistent headache (NDPH) is a form of chronic daily headache (CDH) that may have features of both migraine and tension-type headache. In contrast with other types of CDH, NDPH is characterized by patients recalling the specific date their unremitting daily headache began. In comparison, chronic tension-type headache and chronic migraine are preceded by a gradually increasing frequency of headache. After several months, all three of these CDH forms often have a similar phenotype, making early history a key to diagnosing NDPH. Evaluations to exclude secondary causes are necessary but usually negative. NDPH is difficult to treat and requires a multimodal approach. Questions regarding NDPH remain unanswered. Additional prospective studies are necessary to further understand, characterize, diagnose, and treat NDPH.