Less than 200 cases of posttraumatic superficial temporal artery pseudoaneurysm have been described in the literature. The majority of these cases result from blunt head trauma and are diagnosed an average of three weeks following the inciting traumatic event. In this case report, we describe a superficial temporal artery pseudoaneurysm that developed and was diagnosed the same day of a blunt head trauma in a 54-year-old white male. This is the earliest formation/diagnosis of post-traumatic superficial temporal artery pseudoaneurysm yet reported in the literature. This case report demonstrates that this diagnosis should be kept in the list of differential diagnoses for a post-traumatic soft tissue mass of the face, even immediately following the traumatic event.