We compare American and Korean reactions to the persuasiveness of environmental advertising campaigns. Findings indicate that the effectiveness of the message assertiveness varies depending on recipients’ cultural backgrounds. Study 1 demonstrates that among Americans an assertive recycling message that contains imperatives such as should, must and ought is less effective than a non-assertive message that contains terms such as could, might and worth, yet among Koreans such reactance-driven boomerang effect is not observed. Study 2 extends the findings by conceptually replicating this finding in a different context—energy saving campaign—and further shows that perceived threat to freedom mediates the effects