Socioeconomic inequalities and lack of private health insurance have been viewed as significant contributors to health disparities in the United States. However, few studies have examined their impact on physical functioning over time, especially in later life. The current study investigated the impact of socioeconomic inequalities and lack of private health insurance on individuals’ growth trajectories in physical functioning, as measured by activities of daily living. Data from the Health and Retirement Study (1994–2006) were used for this study, 6519 black and white adults who provided in-depth information about health, socioeconomic, financial and health insurance information were analysed. Latent growth curve modelling was used to estimate the initial level of physical functioning and its rate of change over time. Results showed that higher level of income and assets and having private health insurance significantly predicted better physical functioning. In particular, decline in physical functioning was slower among those who had private health insurance. Interestingly, changes in economic status, such as decreases in income and assets, had a greater impact on women’s physical functioning than on men’s. Black adults did not suffer more rapid declines in physical functioning than white adults after controlling for socioeconomic status. The current longitudinal study suggested that anti-poverty and health insurance policies should be enhanced to reduce the negative impact of socioeconomic inequalities on physical functioning throughout an individual’s life course.