The Dark Factor of Personality (D) measures the latent core of antagonistic traits. The present study evaluated the psychometric properties of the Swedish version of the full (D70) and the brief (D16) versions, concerning structural validity, item information, and convergent validity. An online sample (N = 294) was analyzed using CFA (Maximum Likelihood Estimation), IRT (Graded Response Model) and SEM (latent correlations). Firstly, the original theorized bifactor model for D70 and a single-factor model for D16 showed good fit to the data. Moreover, new reliability-analyses based on FD and H indicated that the D70 favorably can be collapsed into a unidimensional measure, which is further discussed. Secondly, the IRT-analyses present valid item quality and functioning and showed that items provide the most information on trait levels above mean levels. Lastly, convergent SEM-analyses showed that D had high latent trait correlations to psychopathy and Machiavellianism, but not to narcissism. The correlations with the Big Six personality factors (mini-IPIP6) yielded expected high correlations with Agreeableness and Honesty-Humility. The Swedish translation of the full D70 and brief D16 is recommended for use in future research.