Although ambivalence is a long-standing topic of interest in the social sciences, leader-member exchange (LMX) ambivalence and other measures of ambivalence in work settings have only recently attracted attention in the Management literature. To enhance our understanding of the nature of LMX ambivalence, this research investigated specific dispositional antecedents of LMX ambivalence, and whether and how it may influence employee work-related well-being. Using a two-wave design, survey data were collected from employees and their supervisors in a large public organization. Results revealed that specific personality traits, including both supervisor dominance- and prestige-seeking and employee hostility, were significant predictors of LMX ambivalence. Furthermore, LMX ambivalence was found to be significantly associated with two focal measures of work-related well-being: work engagement and emotional exhaustion. Moderated mediation analyses indicated that these relationships were mediated by employee psychological need fulfillment; however, these effects were contingent on two moderating factors - employee collectivism, and perceived meaning in one's work. Overall, these results suggest that supervisor and subordinate dispositional characteristics may contribute to the development of LMX ambivalence. Moreover, complementing previous work (Lee et al., 2019), these findings signal that LMX ambivalence contributes unique variance in predicting employee key work outcomes beyond traditional operationalizations of LMX. Further research is needed testing the nomological net surrounding LMX ambivalence, and when and how LMX ambivalence affects different employee attitudes and behaviors.