Social norms are crucial drivers of human behavior. However, misperceptions of others’ opinions may sustain norms and conforming behavior even if a majority opposes the norm. Privately shifting individuals’ beliefs about true societal support may be insufficient to change behavior if others are perceived to continue to hold incorrect beliefs (“lack of mutual knowledge”). We conduct a field experiment with 5,201 women in Kyrgyzstan to test whether creating mutual knowledge about social norms affects how perceived social norms influence behavior. We show that providing information about societal support for female political activism alone does not affect women’s political engagement. However, when perceived mutual knowledge is created, the effect of information about social norms increases significantly. Using vignette experiments, we show that the effect of mutual knowledge on social punishment is a plausible mechanism behind the behavioral impact. These findings suggest that higher-order beliefs about social norms are an important force linking social norms and behavior.