Objectives To compare the likelihood of receiving an influenza immunization in older adults before and immediately after a cancer diagnosis occurring in 2001 and for the same time periods with older adults not diagnosed with cancer. Design Retrospective analysis comparing influenza immunization rates of Medicare beneficiaries with and without a diagnosis of cancer. Setting Surveillance, Epidemiology, and End Results-Medicare Data. Participants Propensity score matching matched a group of 35,229 persons without cancer with 35,257 individuals diagnosed with cancer in 2001. Measurements Receipt of influenza vaccination based upon Medicare Claims Data. Results A difference-of-difference analysis revealed that influenza immunization rates increased over time for persons diagnosed with cancer (46.8% before to 50.8% after cancer diagnosis), but the increase was greater in beneficiaries without a cancer diagnosis (42.6% to 79.7%) (P <.001; 95% confidence interval = 0.320-0.324). Logistic regression analysis revealed that individuals without a cancer diagnosis were 7.25 times as likely to receive an influenza immunization. Conclusion Older adults who have been recently diagnosed with cancer receive influenza immunizations at much lower rates than older adults who have not been diagnosed with cancer despite interaction with healthcare providers. Opportunities exist to improve influenza immunization in this population, who are susceptible to influenza because of compromised immune systems. © 2012, The American Geriatrics Society.