Many societies are grappling with how to reduce high levels of economic inequality. Although often overlooked, labor unions can have significant flattening effects on inequality. However, unions are not highly supported by the general public. To provide some psychological explanation as to why this may be the case, we examined five potential predictors of general union attitudes (i.e., political orientation, prejudice toward union members, meritocratic beliefs, union knowledge and social mobility beliefs). We tested each variable at least twice across three studies (two in the U.S., one in Canada, total N = 1756). Results indicated that stronger political conservative orientation, prejudice feelings towards union members and less accurate knowledge of union activities uniquely explained lower pro-union attitudes across studies. Meritocratic and social mobility beliefs did not meaningfully explain union attitudes. Although mostly correlational, this research provides insight into potential reasons why everyday citizens may support or condemn unions in an increasingly unequal world. Implications for altering union attitudes and support for related policies are discussed.