Social relationships play a crucial role in shaping the health and well-being of older adults. Despite extensive research on the benefits of social connectedness, changing social and demographic trends require a reassessment of how we measure and understand these relationships. Utilizing data from the National Social Life, Health, and Aging Project (NSHAP), this dissertation explores potential changes in social connectedness to provide a nuanced understanding of their implications for older adults' well-being. The first study examines the distinct role of in-person contact in maintaining healthy behaviors during the COVID-19 pandemic. The findings reveal that decreases in in-person interactions are associated with worsening health behaviors, even with increased use of remote modes of contact, underscoring the unique importance of in-person interactions for older adults’ health and well-being. The second study investigates the links between marital history and the availability and stability of parent-child ties. The results show that remarried older adults generally have more unstable ties with their children compared to those who are continuously married or widowed. The study highlights that cumulative marital transitions can disrupt intergenerational network ties, potentially leading to social disconnectedness from children. The final study explores cohort differences in social connectedness and their association with mental health outcomes among Baby Boomers. Baby Boomers reported lower support from family and friends and higher family strain compared to the Silent Generation. Social relationship quality partially accounted for Baby Boomers’ poorer mental health, suggesting that a decline in social connectedness in terms of relationship quality may contribute to these mental health issues. In sum, these studies show the evolving nature of social relationships among older adults and emphasize that understanding how social connectedness varies over time and across different contexts is essential for promoting health and well-being in later life.