Grit and the Big Five Inventory (BFI) Conscientiousness dimension were examined with respect to the transtheoretical model (TTM) stages of change for exercise behavior. Participants (N = 1171) completed an online survey containing exercise-related TTM staging questions, the Short Grit Scale and BFI Conscientiousness. Ordinal regression analyses showed that grit significantly predicted high intensity and moderate intensity exercise TTM stage while BFI Conscientiousness did not. The results suggest that grit is a potentially important differentiator of TTM stage for moderate and high intensity exercise.