Résumé : Abstract Chronotypes are diversely associated with sleep quality and mental health. Eveningness is generally associated with lower sleep quality and with increased risk for mental health complaints. Along with insomnia symptoms, frequent dysphoric dreams might be key elements of disturbed sleep, and may also indicate psychological imbalance. Our cross-sectional online study aimed to examine whether eveningness can be considered as an independent risk factor of poor mental well-being or whether this association is explained by symptoms of insomnia. Secondly, we examined the associations between eveningness and frequent dysphoric dreaming taking into account the influence of mental well-being and insomnia complaints. Method: We released an online survey with Morningness-Eveningness Questionnaire, Athens Insomnia Scale, General Mental Health, and frequency of dysphoric dreaming: nightmares and bad dreams separately. We analyzed the data of 2077 participants (M AGE  = 28.5, SD = 9.6). Eveningness showed a weak but independent association with mental well-being. Additional analyses showed no signs of associations between eveningness and dysphoric dreaming, such as nightmares and bad dreams. The frequency of bad dreams was associated with insomnia complaints and mental well-being, but nightmare frequency was only linked to insomnia symptoms, but not to mental well-being. Insomnia complaints emerged as a more robust factor in poorer mental well-being than the eveningness preference. Eveningness was not associated with dysphoric dreaming. Restoring insomnia might be essential in individuals at risk for mental health complaints.