This study aimed to explore how dark personality traits influence the interplay between embitterment and jealousy. We first assessed the appropriateness of the scales used to assess jealousy, personality, and embitterment for our study population, examining their performance across different relationship statuses and ensuring their reliability. Then, through correlation, regression, and moderation analyses, we investigated the relationships among these measures. Our results revealed that Machiavellianism and narcissism act as moderators in the embitterment–jealousy relationship. Specifically, Machiavellianism moderated associations between overall embitterment and its psychological state and behavioral jealousy, while narcissism moderated connections between total embitterment and its psychological state, behavioral jealousy, cognitive jealousy, and overall jealousy. Furthermore, the combined influence of a longer relationship duration and higher levels of embitterment and Machiavellianism contributed to total jealousy scores. These findings deepen our comprehension of jealousy’s intricacies and the underlying factors at play.