Objectives: Medication-overuse headache (MOH) is recognized as a biobehavioural disorder, warranting that both biological and psychological factors are targeted throughout treatment. A psychological factor of importance may be personality that could be used to tailor treatment if differences are found across headache diagnoses. The objectives were as follows: (a) To investigate if migraine patients and patients with MOH differed on personality traits, (b) To investigate if the two headache groups differed from a Danish normative sample, with respect to personality traits. Materials and Methods: The NEO-Five-Factor Inventory was completed, and an age-matched cohort of episodic migraine patients (n = 94) and MOH patients (n = 94) was included. Multivariate regression models and sex-stratified comparisons were made on patients’ raw scores from five personality traits; neuroticism, extraversion, openness, agreeableness, and conscientiousness. The headache groups were also compared to personality traits from a Danish normative sample (n = 1032). Results: MOH females obtained significantly lower scores on extraversion (24.4 ± 4.3 vs 27.1 ± 7.2, P < 0.01), openness (23.7 ± 3.9 vs 26.2 ± 6.4, P < 0.01), and conscientiousness (28.9 ± 3.7 vs 34.6 ± 5.8, P > 0.01) as compared to female migraineurs. Males showed no differences. Compared to the normative sample, both headache groups showed a lower score on extraversion (P < 0.01). Furthermore, MOH patients had statistically significant lower scores on conscientiousness while the migraine patients had a higher score. Conclusion: Results suggests some personality trait differences between migraine and MOH patients. Especially, females showed different personality traits, where the MOH females appeared more introvert and less socially orientated. If confirmed in larger studies, this information could be used in personalized treatment in clinical practice.