Background: Controversy has emerged about cardiovascular benefits versus harms of dairy fat consumption. Further, little data are available on potential long-term noncardiovascular effects. In addition, most observational studies to date assessed self-reported estimates of dairy fat consumption, which may not capture all dietary sources; and the few studies using objective biomarkers included only one baseline measure, which may lead to poor estimation of long-term risk. Aims: To investigate prospective associations of serial measures of dairy plasma phospholipid fatty acids (15:0, 17:0, trans 16:1n-7) with cause-specific and total mortality among older adults in the Cardiovascular Health Study. Methods: Among 2,638 U.S. adults aged ≥65y and free of CVD at baseline, circulating fatty acid levels were measured serially at baseline, 6 years and 13 years using standardized methods. All-cause and cause-specific deaths were assessed and adjudicated centrally. Prospective associations were assessed by multivariate-adjusted Cox models incorporating time-dependent fatty acid measures and covariates. Results: During 36,486 person-years of follow-up (1992-2015), 2,619 deaths occurred (930 CVD deaths, 1,689 non-CVD deaths), with 603 CHD deaths and 208 stroke deaths. After adjustment for demographic and lifestyle factors, higher plasma phospholipid 17:0 and trans 16:1n-7 were associated with lower cause-specific and total mortality (see Table). There were no statistically significant associations with 15:0. Conclusion: Plasma phospholipid 17:0 and trans 16:1n-7, two objective biomarkers of dairy fat consumption, measured serially over 13 years, were associated with lower all-cause and especially CVD mortality among older adults. A third biomarker, 15:0, was not significantly associated with mortality. These novel findings highlight the need for detailed mechanistic and interventional investigation of long-term health effects of dairy fat, dairy-specific fatty acids, and dairy foods.