Life satisfaction predicts lower risk of adverse health outcomes, including morbidity and mortality. Research on life satisfaction and risk of dementia has been limited by a lack of comprehensive clinical assessments of dementia. This study builds on previous research examining life satisfaction and clinically ascertained cognitive impairment and dementia. Participants (N = 23070; Mean = 71.83, SD = 8.80) from the National Alzheimer's Coordinating Center reported their satisfaction with life at baseline. Incident dementia was ascertained through clinical assessment over up to 18 years. Life satisfaction was associated with about 72% lower risk of all-cause of dementia, an association that remained significant accounting for demographic (age, sex, race, ethnicity, education, marital and living status), psychological (depression), clinical (obesity, diabetes, hypertension), behavioral (current and former smoking), and genetic risk (APOE ϵ4) factors. The association was not moderated by demographics, depression, and APOE ε4 status groups. The association was similar when cases occurring in the first five years were excluded, reducing the likelihood of reverse causality. Life satisfaction was also linked to specific causes of dementia, with a reduced risk ranging from about 60% to 90% for Alzheimer's disease and vascular dementia to > 2-fold lower risk of Lewy Body and frontotemporal dementia. Older adults who were satisfied with their lives were also at 61% lower risk of incident mild cognitive impairment and at 22% lower risk of converting from mild cognitive impairment to dementia. Being satisfied with one's life is associated with a lower risk of dementia. Improving life satisfaction could promote better cognitive health and protect against dementia.