As a trait-like disposition, optimism has received a wealth of research attention in connection with areas of physical and psychological well-being. However, less research attention has focused explicitly on the stability of optimism during adulthood. As such, we currently know very little about the long-term stability of optimism during middle adulthood, the developmental changes in optimism that occur across adulthood, or whether optimism changes in relation to specific life event experiences. The present research addressed these gaps in the optimism literature by examining stability and changes in optimism and pessimism over approximately nine years using longitudinal data from a sample of African American adults participating in the Family and Community Health Study (FACHS). In addition, this research attempted to extend adaptation theory as a potential explanation for short-term and/or long-term changes in optimism and pessimism following life event experiences. In terms of general stability, optimism and pessimism demonstrated moderate rank-order stability over time. However, average levels of optimism and pessimism increased and decreased, respectively, across the nine-year study period. Although not entirely consistent, life event experiences did relate to reactive changes in both optimism and pessimism in specific instances. Finally, effect size estimates for adaptive changes following life event experiences were generally consistent with complete adaptive recovery processes, except for a potential exception involving changes following marriage. Discussion integrates the study findings with the literature on personality development in adulthood, the stability of optimism and pessimism, and adaptation theory, with focus on potential implications of these findings for future research efforts aimed at integrating dominant theoretical perspectives in personality psychology.