The objective of this research was to validate the Narcissistic Personality Inventory across different response formats, given that several factor structures were proposed, ranging from two to seven factors. The original forced-choice format of the Narcissistic Personality Inventory was given to 410 participants and a modified, i.e., Likert format was given to 423 participants from the general population, along with personality and other narcissism measures. The results showed that the five-factor model proposed by Ackerman et al. had the best model fit in both response formats and that a distinction between adaptive (Leadership, Vanity, and Superiority) and some aspects of maladaptive (Manipulativeness and Exhibitionism) narcissism factors could be established. However, the redundancy of items in certain factors could be problematic and further improvements of the Narcissistic Personality Inventory should include more indicators of some proposed factors, especially of Vanity.