Objectives: Type D personality is characterized by the combination of social inhibition and negative affectivity. This study examined the relationship between Type D personality and insomnia symptoms amongst a sample of the general-population. Methods: Adults from the general-population (n = 392) completed online measures of Type D personality (DS14) and insomnia severity. Results: Individuals with the Type D personality trait reported significantly greater symptoms of insomnia relative to Non-Type Ds. Moreover, insomnia-symptoms were independently related to negative affectivity (NA) and social inhibition (SI) and the Type D interaction (i.e. synergistic product of SI and NA). Linear regression analysis determined that NA but not SI significantly predicted insomnia symptoms after controlling for age and sex. However, after accounting for the Type D interaction, negative affectivity remained the only significant predictor of insomnia-symptoms. Conclusions: The Type D personality type appears to be related to insomnia-symptoms, both as a categorical and dimensional construct. These outcomes support prior research evidencing that whilst Type D personality is related to poor sleep in adolescents, NA appears to be the main contributor.