The present study investigates how stereotypes influence impression formation in direct social interactions and explores an intervention to reduce their effects. Although perceivers can form impressions of others in direct interaction based on feedback, via instrumental learning, stereotypes have been shown to distort this process, leading to the formation of biased impressions. Since instrumental learning occurs implicitly, individuals may be unaware of the stereotype-driven biases shaping their perceptions. Drawing from learning and memory research, this study proposes a counter-stereotypical intervention to weaken stereotype effects before they influence instrumental learning. Participants interacted with players from two groups, described with either positive or negative stereotypes, in an online money-sharing game. In the intervention condition, participants additionally received counter-stereotypical information about the negatively described group prior to their interactions. Results showed that, despite equated sharing rates between members of each group, participants in the control condition formed more positive impressions of players from positively stereotyped than negatively stereotyped groups, whereas this stereotype effect was reduced in the intervention condition. These findings provide insight into how explicit societal stereotype messages become internalized through learning mechanisms and inform strategies for prejudice reduction.