As text-based computer-mediated communication (CMC) supported by affective technology becomes increasingly common in our daily life, new opportunities for the communication of critical information, such as negative feedback, arise. Research on affective technology has already shown that the acceptance of negative feedback can be improved by using emoticons under specific conditions. However, in which way emotion recognizing affective technology can increase the acceptance of negative feedback automatically is still unclear. We hypothesized that automatically reported stress and a low stress level increases feedback acceptance and its predictors. Additionally, we hypothesized an interaction effect that could attenuate the negative effect of high stress when the stress level is automatically detected. Using a messenger that reports the feedback provider’s stress level to the feedback recipient, we investigate how the automaticity of stress detection and the displayed stress level can increase negative feedback acceptance and its predictors. We conducted a 2 (stress level: low vs. high) × 2 (automaticity: automatically detected vs. self-reported) + 1 (control group) between subjects laboratory experiment, resulting in five experimental groups. Our results show that whereas an automatically detected stress level increases perspective taking, seeing a low stress level increases perceived good intention.