Background: Conscientiousness can predict participation in physical activity. A facet of conscientiousness that may contribute to the organization for physical activity is planfulness. Planfulness may be a determinant of planning behavior for physical activity. The relationship between dispositional needs to plan (planfulness), intentions to plan, perceived control over planning, planning behavior and physical activity have yet to be investigated. The purpose of the present study was to determine if planfulness moderated the relationship between intentions to plan and planning behavior for physical activity. The secondary objective was to test if planfulness moderated the relationship between planning behavior and physical activity. Methods: Participants were adults (n = 337, Mage = 31.0 ± 5.2 years) with intentions to be active. Participants reported planfulness, perceived behavioral control over planning, intentions to plan, planning behavior, physical activity intentions and physical activity behavior at baseline (T1) and after 1 month (T2). Moderation analyses were conducted using hierarchical regressions. Results: After controlling for trait planfulness, cognitions toward planning and previous planning behavior, the interaction between planfulness and intentions to plan was significant (R2Δ = 0.02, P < 0.05). Intentions to plan were more strongly related to planning behavior for individuals of high planfulness than of moderate or low planfulness, ps<0.01. Planfulness did not moderate the relationship between planning behavior and physical activity, P>0.05. Conclusion: Findings suggest that a disposition toward planning may affect the motivation to plan but not necessarily the implementation of a plan for physical activity.