Background: Chronic pain and disability after whiplash injury is common and causes considerable social and financial costs. Predicting the factors contributing to disability in whiplash injury can facilitate rapid intervention. Objectives: The aim of this study was to examine the effect of mental and behavioral factors on severity of whiplash injury disability two years after the primary insult. Methods: In this analytic cross-sectional study, chronic complications of whiplash injury in patients were evaluated two years after the insult. Participants were categorized into three groups based on neck disability index scores at 2 years after the injury. Intergroup differences were analyzed and investigated with previous inconsistencies. P values less than 0.05 were considered statistically significant. Results: A total number of 81 patients were investigated in our study. Patients were categorized into the "recovered", "mild pain and disability" and "moderate/severe pain and disability" groups. There was no statistically significant relationship between three groups regarding the treatment method. Our results showed a statistically significant difference between the personality type and severity of disability (P = 0.031). The Beck depression score was not significantly different between the three disability groups. Conclusions: Type B personality and primary presence of moderate stress symptoms after trauma can predict strongly the poor outcome at 2 years after injury. These factors should be evaluated in people with acute whiplash injury. Appropriate treatment based on these factors may help to reduce chronicity and related complications.