Mental toughness (MT) has been related to high performance in competitive situations. The current studies tested whether individual differences in MT were associated with success in two achievement domains: higher education and work. Academic performance and attendance were assessed over three years in a British university sample. MT was associated with higher average academic grades (Study 1). Individual differences in MT predicted individuals' income, controlling for age and gender (Study 2). The results suggest that MT entails positive psychological resources that are important for academic and career success. Future research aiming at exploring the factors that contribute to variation in MT and the mechanisms that underlie the association between MT and achievement may have significant implications for predicting and optimizing performance in various domains.