Ambivalence, the simultaneous experience of positive and negative thoughts and feelings regarding an attitude object, plays a crucial role in decision-making. Ambivalence has mostly been assessed through self-reports, reaction times, and also mouse-tracking measures. Recent research assumes that eye-tracking may provide further potential indicators for ambivalence, possibly overcoming some limitations of the currently established measures. However, this has not been validated yet. To do so, we implemented an eye-tracking study using an evaluation task frequently used in ambivalence research: Participants evaluated univalent, neutral, and ambivalent attitude objects as either positive or negative while their eye movements were recorded. After this, they evaluated the same stimuli with their mouse movements recorded, and finally, they rated the stimuli on different self-report measures of ambivalence. We expected that ambivalent stimuli elicit more fixation transitions and increase pupil dilation compared to neutral and univalent stimuli. Furthermore, these eye-tracking measures should correlate with the established measures of ambivalence. The results of a first preregistered study (N = 84) will be presented and their implications for assessing ambivalence in psychological research will be discussed.