The number of older adults is expected to increase in the near future. Since women live longer than men, women tend to have more complex social networks than men, and women report higher rates of depression than men, it is important to determine whether gender and social isolation affect the rates of depressive symptoms reported by older adults. This thesis seeks to determine the relationship between gender and social isolation and the influence of these variables on depressive symptoms in older adults using selected data from two sections of the 2012 wave of the Health and Retirement Study (HRS). Ordinary least squares (OLS) regression was performed in SPSS in order to determine the main effects relationship between the dependent variable, depression, and independent variables, gender and social isolation. Two additional models were examined to test whether social isolation had a mediating and/or moderating effect on gender's relationship to depressive symptoms. As expected, women average more depressive symptoms than men; however, several aspects of social support, such as living with a spouse or partner, contact with children, contact with friends, and neighborhood cohesion, decreased depressive symptoms. Contact with children, contact with friends, and neighborhood cohesion moderated depressive symptoms. All five social isolation variables -- living with a spouse or partner, contact with children, contact with family, contact with friends, and neighborhood cohesion -- mediated depressive symptoms for gender. These results suggest that social isolation not only has a direct effect, but also moderates and mediates depressive symptoms for gender. This research supports the hypothesis that depressive symptoms are associated with gender and social isolation.