Postconcussion symptoms (PCS) are not uncommon following mild traumatic brain injury (mTBI). Personality traits have always been viewed as one of the most important explanations for persistent postconcussion symptoms (PPCS). Unfortunately, studies on the association between preinjury personality traits and the PPCS are still limited. This study thus aimed to examine the relationship between the preinjury personality and PCS in patients with mTBI. A total of 106 participants including 53 healthy participants were recruited. All participants complete the modified Checklist of Postconcussion Symptoms and the Health, Personality, & Habit Scale. Participants were evaluated within 4 weeks and at 4 months, respectively, after injury. The results showed patients reported significantly more PCS than healthy participants did within 4 weeks postinjury. A significant positive association between PCS and retrospectively evaluated preinjury personality was found. Specifically, patients who reported that their preinjury personality was depressive or anxious-related presented more PCS. This study might be the first to directly demonstrate that preinjury personality traits are closely linked to PCS reporting in patients with mTBI. Importantly, PCS reporting might be associated with different personality traits at different periods after injuries, and thus, a careful evaluation for personality characteristics is merited after mTBI.