Research on attitudinal ambivalence started in the early 1970s, forty years after the first wave of research on attitudes. Ambivalent attitudes consist of both positive and negative evaluations of the same object. Early approaches proposed different measurement methods, and ambivalence can now be measured either directly (referred to as “felt ambivalence”) or indirectly (referred to as “potential ambivalence”). Because of its duality, ambivalence has been studied in comparison with univalent attitudes—which consist of either positive or negative evaluations of an object—to uncover their specific features, antecedents, and consequences. Relevant research has focused on identifying the prevalence of ambivalent attitudes, and on whether they could stem from particular personality traits or situations. Researchers have found that ambivalent attitudes seem to be widespread and can be held for a long period of time. Their relationship with behaviors has also been widely studied. At the individual level, ambivalence increases response latency when a choice has to be made, extends information processing, can affect attitude stability, and can even lead to discomfort. At the behavioral level, studies have highlighted the moderating role of attitudinal ambivalence on the relationship between attitudes and behavior. A different field of research focuses on its strength to question whether ambivalence leads to more resistance or susceptibility to persuasion and influence. It appears that ambivalent attitudes are pliable and, depending on the context, can either help individuals to be more adaptive or prevent them from arriving at a satisfying conclusion. The role of ambivalent attitudes in interpersonal relationships and self-presentation also highlight some benefits in holding an ambivalent attitude. This article opens by reviewing general overviews to provide a detailed picture of the current state of research. It then presents early approaches to attitudinal ambivalence, and reviews studies that highlight the moderating role of attitudinal ambivalence on the relationship between attitudes and behavior, as well as studies that question whether ambivalence might lead to more resistance or susceptibility to persuasion and influence. The article then focuses on the impact of ambivalence at the individual level. Antecedents of attitudinal ambivalence will be reviewed, as well as its consequences on the individual. The article concludes by presenting research questioning its functions as well as some applied work.