Objectives While it has been proposed that certain personality traits are predisposing factors for insomnia, the nature of these traits and mechanisms through which they contribute to insomnia has been understudied. Methods In the present study, 88 participants with self‐reported insomnia took part in an online assessment of normal personality functioning, insomnia severity, sleep‐related cognitive distortions, pre‐sleep arousal, and negative affect. Results Participants scored high on personality measures of neuroticism and openness, and low on conscientiousness, relative to a normal sample. Neuroticism was found to relate to insomnia severity through the mediating effects of sleep‐related cognitive distortions, pre‐sleep arousal, and to a much lesser degree negative affect. Conclusions These results further support the notion of neuroticism being a predisposing factor for insomnia, suggest a pathway for this relationship, and may have implications for individual responses to the treatment of insomnia.