Determining whether Need for Cognition (NC) has the same meaning across age may help understand why there are dramatically different age trends for cognitive abilities and for NC in adulthood. Data from 5,004 participants aged between 18 and 99 years were used to examine both internal relations and external relations of NC. Internal relations were investigated with measures of reliability, examination of factor invariance, and test–retest coefficients across three age groups. External relations were investigated by examining relations of NC with cognitive abilities, engagement, personality, self-rated cognition, and affect. Results suggest that NC may be a broad construct that could reflect motivation to seek out intellectual challenge. In addition, examination of both internal and external relations of NC indicated that the meaning of the construct may be the same across the life span. Finally, the current article showed that the strongest predictor of NC was Openness to Experience, at any age.