Parent support for physical activity (PA) is a behavior unto itself that requires motivation. Persuasive messages may be one method for motivating parent support for their children’s PA. Message framing is one strategy for optimizing the impact of messages. The current study examined the relative effectiveness of gain- versus loss-framed messages for encouraging parent support for children’s PA. Regardless of message frame, parents had an increase in social cognitive antecedents (e.g. perceived behavioral control, intentions) and support for children’s PA following message exposure.