Objectives: Goal intentions are the key proximal determinant of behavior in a number of key models applied to predicting health behavior. However, relatively little previous research has examined how characteristics of goals moderate the intention–health-behavior relations. The present research examined the effects of goal priority and goal conflict as moderators of the intention–health-behavior relationship. Method: The main outcome measures were self-reported performance of physical activity (Studies 1, 2, and 3) and other health behaviors (Study 4), and objectively measured physical activity (Study 3). Studies 1 and 4 used prospective correlational designs to predict later behavior from earlier cognitions. Studies 2 and 3 were experimental studies manipulating goal priority and goal conflict. Studies 1 and 2 used between-subjects designs while Studies 3 and 4 used within-subjects designs. Results: Goal priority significantly moderated the intention–health-behavior relationship for physical activity (Study 1) and a range of protective and risk health behaviors (Study 4). Manipulations of goal priority significantly increased the intention–physical-activity relationship when self-reported (Study 2) and objectively measured (Study 3). In contrast, inconsistent effects were observed for goal conflict as an intention–behavior moderator. Conclusions: When goal priority is high, then intentions are strong predictors of health behaviors. Further studies testing manipulations of goal conflict and in particular goal priority in combination with goal intentions are required to confirm their value as a means to change health behavior.