Background: Individuals receiving healthcare services often experience differential treatment based on their personal identity characteristics (e.g., age, race, gender), including in the context of shared decision making with clinicians. Yet, little is reported about the extent of bias experienced by family and friend caregivers from the clinician support they and patients receive when making cancer-related decisions. Methods: Analysis of data from a nationally-representative U.S. online survey conducted by CancerCare (2/2021-7/2021) of family caregivers of patients with cancer (N = 2,703). Bias experienced in decision support was assessed with the item: “Have you felt that the support you and the person with cancer have received for making cancer-related decisions by your doctor or healthcare team has been negatively affected by any of the following?” Check-all-that-apply response options included: age, race, language, education, political affiliation, body weight, insurance type or lack of insurance, income, religion, sexual orientation, and gender/sex. Chi-square was used to compare demographics and bias; regression analyses were used to identify relationships between bias and caregiver’s psychological distress, measured by the GAD-2 and PHQ-2. Results: Out of 2,703 cancer caregiver respondents, 47.4% (n = 1,281) reported experiencing at least one type of bias when receiving healthcare team support for making cancer-related decisions, with body weight (24.7%), age (22.2%), and income level (19.9%) being the most commonly endorsed biases. Experiencing one or more types of bias differed by caregivers’ age (p <.001; younger > older), gender (p <.001; male and transgender/gender nonconforming > females), race (p <.01; African American/Black and Alaskan Native, American Indian, Native Hawaiian, or Pacific Islander > White and Asian), ethnicity (p <.001; higher for Hispanic/Latino), education (p <.01; higher education > less education), and length of time providing care (p <.01; higher for longer time providing care). After covariate adjustment, the odds of having high anxiety (GAD-2 scores≥3) were 3 times higher for caregivers experiencing ≥1 types of bias compared to those experiencing none (adjusted OR, 3.12; 95% CI, 2.6-3.7); similarly, the odds of having high depression symptoms (PHQ-2 scores≥3) were also 3 times higher (adjusted OR, 3.29; 9% CI, 2.8-3.9). Conclusions: Half of caregivers involved in their care recipients’ cancer-related decisions report bias in the decision support received from the healthcare team. Furthermore, experiencing bias was associated with increased odds of experiencing psychological distress. The pervasiveness of bias experienced by families involved in patients’ cancer-related decisions suggests the priority need to critically evaluate and improve clinician decision support practices.