<p>The rising income inequality across advanced and developing countries has prompted many discussions about tax progressivity that aims at increasing the taxes paid by high-income individuals. Studies have shown that the experiences of being exposed to socioeconomic heterogeneity are particularly important in sculpting the inferential accounts of unequal outcomes and future prospects. However, less is known about how upward and downward social interactions shape individuals’ preferences for tax progressivity by influencing their beliefs about the prospects of upward mobility and fairness. Based on the theoretical concepts of contact hypothesis and lived experiences, this research fills this gap by exploring how social interactions affect people’s perceptions about inequality and mobility that potentially shape their attitudes toward tax policy. Using large-scale cross-country data of the 2019 International Social Survey Programme (ISSP), it analyzes whether upward (downward) social interactions (i.e., contacts with richer (poorer) others) influence individuals’ beliefs of fairness and prospect of upward mobility and consequently shape their preferences for tax progressivity. The results from multilevel mixed models and causal mediation analysis indicate that the prospect of upward mobility negatively correlates to tax progressivity, and that perceived unfairness increases the support for a more progressive tax policy. These findings show that downward social interaction has stronger indirect effects on preferences for tax progressivity than upward social interaction. They suggest that a higher frequency of downward social interactions can potentially increase high-income individuals’ empathic concerns about the difficulties of poorer others and enhance their perceptions of unfairness conditions and support for tax progressivity, but the effects of upward social interactions are either insignificant or relatively weaker.</p>