Gynecologic cancers are an important problem in older American women. These patients may experience significant physical and mental problems that negatively impact their health-related quality of life (HRQOL). While HRQOL is becoming an increasingly important part of cancer research, relatively little is known about HRQOL in older women with gynecologic cancers. The objective of this dissertation was to characterize HRQOL in older American women with gynecologic cancer using the Surveillance, Epidemiology, and End Results – Medicare Health Outcomes Survey (SEER-MHOS) linked data resource. We identified female Medicare Advantage Organization enrollees who were at least 65 years old when diagnosed with a first primary invasive cervical, ovarian, or uterine cancer and participated in MHOS between 1998 and 2014. The three research studies in this dissertation each addressed a different aspect of HRQOL in older gynecologic cancer patients. The first study assessed the impact of depressive symptoms on HRQOL in women with gynecologic cancer versus matched cancer-free controls. We found that women with cancer were significantly more likely to screen positively for depression and that women with cancer and depressive symptoms had significantly worse HRQOL than cancer-free controls and women with no depressive symptoms. The second study evaluated the likelihood of developing functional impairments after cancer diagnosis and estimated pre- to post-diagnosis changes in HRQOL in women with cancer compared to a matched group of women without cancer. We determined that cancer patients, particularly those diagnosed at advanced stages, had significantly greater odds of functional impairment and experienced greater declines in HRQOL compared to controls. The third and final study examined the association between HRQOL, functional impairments, and depressive symptoms measured before cancer diagnosis with survival in older women with endometrial cancer. We observed that both physical and mental aspects of HRQOL were associated with survival and that women with worse HRQOL had significantly worse prognosis. Together these studies provide evidence of the significant impact that gynecologic cancer has on both physical and mental aspects of HRQOL in older women, and they underscore the need for tailored interventions to reduce pain, provide support, and prepare older women for changes in functioning and health after diagnosis with gynecologic cancer. Further, these findings demonstrate the value of HRQOL and other patient-reported outcomes in cancer research, as many physical and emotional problems cannot be measured by traditional laboratory tests. HRQOL measures can thus be used to better identify women with cancer who are at greatest risk of declining health, functional impairment, and depression. Assessment of HRQOL in cancer patients may help providers routinely monitor changes in physical and mental well-being, inform treatment decisions, and determine appropriate supportive care.