Affective judgments of physical activity have emerged as important predictors of physical activity and interventions targeting affective judgments are a promising approach to improving regular physical activity. Currently, measures assessing a variety of potentially distinct constructs are treated as interchangeable assessments of affective judgments of physical activity. Moreover, little is known about the construct validity of the purported measures of this construct. We review several components of construct validity; highlighting their importance for health psychology research. Then, we examine the construct validity of a wide variety of affective judgment of physical activity measures in MTurk and student samples. Cronbach’s alpha for the included measures was uniformly high; however, several scales contained excessively redundant items that ultimately lessen their construct validity. Moreover, dependability estimates for the majority of measures was poor, indicating high levels of transient measurement error. The included measures significantly predicted levels of physical activity; however, their relative predictive power was strongly associated with their dependability. In general, the affective judgment measures demonstrated poor convergent validity suggesting they are not interchangeable and best viewed as assessing distinct, albeit related, constructs. Another important limitation of these measures is that they exhibited poor discriminant validity from exercise self-efficacy, which represents an important theoretical and empirical issue for the field of health behavior research. Overall, the current findings indicate the available affective judgments of physical activity measures are suboptimal, have considerable construct validity limitations, and thereby prevent the further advancement of science, theory, and intervention development in this promising area of research.