Mild traumatic brain injury (mTBI) and concussion are terms often used interchangeably. However, mTBI is frequently seen as representing a broader injury that encompasses the construct of concussion, which often conveys transience or decreased severity. The present study examined the influence of varying diagnostic terminology on acute injury expectations in an undergraduate population (N=105). Participants were presented with an mTBI vignette and were randomly assigned to one of two conditions in which the term mTBI or concussion was used to describe the injury. There were no significant differences between the two conditions on anxiety, symptomatology, timeline, or consequence scales. However, participants in the mTBI group allocated more days to return to play than participants in the concussion group, suggesting that terminology has an effect on perceptions of the severity of the injury. Varsity athletes allocated fewer days to return to play than nonathletes. Individuals with a history of concussion, both athletes and nonathletes, indicated fewer days to return to play, but greater symptomatology than individuals with no history of concussion. Clinicians should consider the influence of diagnostic terminology, athletic background, and history of concussion on perceptions of the severity of an injury because expectations can influence injury outcomes and compliance in a recovery process.