A collective constructionist theory of the self proposes that many psychological processes, including enhancement of the self (pervasive in the United States) and criticism and subsequent improvement of the self (widespread in Japan), result from and support the very ways in which social acts and situations are collectively defined and subjectively experienced in the respective cultural contexts. In support of the theory, 2 studies showed, first, that American situations are relatively conducive to self-enhancement and American people are relatively likely to engage in self-enhancement and, second, that Japanese situations are relatively conducive to self-criticism and Japanese people are relatively likely to engage in self-criticism. Implications are discussed for the collective construction of psychological processes implicated in the self and, more generally, for the mutual constitution of culture and the self.