Background Adequate social support for older adults is necessary to maintain quality of life and reduce mortality and morbidity. However, little is known regarding the social support needs of older adults with cancer. The objective of the current study was to examine social support needs, specifically the unmet needs, among older adults with cancer. Methods Medicare beneficiaries (those aged ≥65 years) with cancer were identified from the University of Alabama at Birmingham Health System Cancer Community Network. Social support needs were assessed using a modified version of the Medical Outcomes Study Social Support Survey. The authors defined an “unmet need” if participants reported having some/a little/never availability of support and requiring support for that need. Results Of the 1460 participants in the current study, the average age was 74 years (standard deviation, 5.8 years). Approximately two‐thirds of participants (986 participants; 67.5%) reported having at least 1 social support need, with the highest needs noted in the emotional (49.5%) and physical (47.4%) support subdomains. Of those individuals with a support need, approximately 45% had at least 1 unmet need, with the greatest percentages noted in the medical (39%) and informational (36%) subdomains. Multivariable analyses demonstrated that participants who were nonwhite, were divorced or never married, or had a high symptom burden were at greatest risk of having unmet social support needs across subdomains. Conclusions In this population of older adults with cancer, the authors found high levels of unmet social support needs, particularly in the medical and informational support subdomains. Participants who were nonwhite, were divorced or never married, or had a high symptom burden were found to be at greatest risk of having unmet needs. The results of the current study demonstrate a high prevalence of social support needs among older adults with cancer, among whom nearly two‐thirds are found to have an unmet social support need. The greatest percentage of unmet support needs are within the medical and informational support domains, and multivariable analyses indicate that nonwhite individuals, those who are divorced or never married, or those with a high symptom burden are at greatest risk of having unmet social support needs across subdomains.