This research aims to examine cross-sectional and longitudinal associations of positive subjective well-being among centenarians and near-centenarians in the Health and Retirement Study. Participants who eventually survived to age 98 or older (<em>N</em> = 516) were included. Study variables included demographic characteristics, health and activities of daily living (ADL) functioning, cognitive functioning, and positive well-being. Additionally, a smaller subsample (<em>n</em> = 192) of participants with supplemental leave-behind questionnaire (LBQ) data, some of whom (<em>n</em> = 30) were assessed across three comparative time points, were included to examine psychological well-being variables over time. In the full sample, approximately 86% and 81% of participants over or near the age of 100 reported enjoying their lives and being happy, respectively. Also in the full sample, better self-rated health (SRH) was associated with greater happiness/enjoyment. Results with the LBQ subsample (<em>n</em> = 192) identified that a) greater life satisfaction related to better SRH, b) better cognitive functioning related to greater optimism and purpose in life, and c) more educated and non-White participants tended to have greater purpose in life. Finally, for the longitudinal subsample, life satisfaction increased significantly while purpose in life decreased significantly as participants neared age 100. Implications for this study include a greater focus on developing interventions geared toward improving psychological well-being; specifically, increasing purpose in life and optimism, as well as focusing on improving happiness and life enjoyment.