Exercise intention is usually considered as the most immediate predictor of future exercise behavior in social cognition models. However, research on the motivational process of exercise (i.e., formation of exercise intention) receives far more attention than the volitional process of exercise behavior (i.e., translation of exercise intention to action). In this study, factors that operate within the volitional process were examined. The moderating effects on the intention-behavior relation, namely intention stability and goal conflict, have been supported empirically in previous studies. The purpose of this study was to examine the relationship between these two moderators under the framework of the Theory of Planned Behavior (TPB). One hundred and thirty-five participants completed a longitudinal study with three waves of data collections, two weeks apart from each collection time. Intention stability was operationalized as the differences between intention measures at Time 1 and Time 2. Exercise behavior at Time 3 was regressed on the TPB variables at Time 2, past behavior, goal conflict, intention stability, and the interactions among intention, intention stability, and goal conflict. Bootstrapping technique was used to obtain more accurate estimates of the standard errors as the distribution of exercise behavior was skewed. Results revealed a significant three-way interaction among intention stability, goal conflict, and behavioral intention on future exercise behaviors (β=-.21 , p<.05). The intention stability has a strengthening effect on the intention-behavior relation. However, if the level of goal conflict is high, the strengthening effect reverses. Specifically, when both the levels of stability and goal conflict are high, the relationship between intention and behavior is weak. People may tend to procrastinate, ruminate, or even avoid taking actions. While the level of stability is low and the level of goal conflict is high, the intention-behavior relation is moderate and it may reflect the accommodating process of behavioral intention to competing goals. Results support the theoretical notion that the intention stability is a temporal property of intention strength and it further suggests that the strengthening effect of intention stability is conditional on the level of goal conflict. Two possible detrimental effects of goal conflict, namely hesitation and accommodation, are identified. Practically, it is suggested that deeper cognitive process (e.g., goal conflict) is involved in taking action to engage in physical activity. For example, strategies for resolving conflicting goals should be emphasized in promoting the participation of physical activity. Keyword(s): health promotion, participatory, physical activity