Abstract Background: Valid consent for research requires that the decision for participation be both fully informed and voluntary. Previous studies on informed consent have shown that when presented with a clinical trial for their child, parents often do not understand the many components of informed consent, including voluntariness of participation. In addition, individuals with limited English proficiency have reported lower understanding and satisfaction during informed consent. There is limited research on factors associated with perception of voluntariness during participation in pediatric cancer clinical trials. Our aim was to examine contextual factors associated to perception of voluntariness in parents who had consented to participation of their child in a clinical trial for cancer treatment, focused on characterizing differences between non-Hispanics and Hispanics, as the latter is the fastest-growing ethnic group in the U.S. Methods: Parents (n=97) of children aged 0-17 years with newly diagnosed cancer, who had consented to participation of their child in a clinical trial for treatment at Rady Children's Hospital-San Diego, were prospectively recruited. Participants completed questionnaires assessing sociodemographics, health literacy, perception of voluntariness, decisional regret, satisfaction, and acculturation level, if Hispanic. Outcomes and their correlates were analyzed using logistic regression. Results: Fifty participants (51.5%) were Hispanic and 47 (48.5%) non-Hispanic. We found that parents who were Hispanic compared to non-Hispanics (p<0.001), Spanish-speaking compared to English-speaking (p=0.048), and those with lower health literacy (p<0.001) had lower perception of voluntariness. Decisional regret was overall low and satisfaction was overall high across all subgroups and neither measure was significantly impacted by sociodemographics, health literacy or acculturation. Conclusions: In this study, with equivalent numbers of Hispanics and non-Hispanics, we found that Hispanic parents of children with newly diagnosed cancer, and particularly Spanish-speakers and those with low health literacy, had inadequate perception of voluntariness. To our knowledge, this is the first study to associate lower health literacy with lower perception of voluntariness in parents of children with newly diagnosed cancer despite overall high rates of satisfaction with the informed consent process for pediatric cancer clinical trials. True voluntariness of participation is essential to the ethical practice of informed consent, and our study suggests that many participants with low health literacy, particularly Hispanics and Spanish-speaking individuals, are not making truly informed decisions. Tailored interventions can improve decision-making, reduce clinical trial participation inequities and, ultimately, eliminate survival disparities by effectively and equally translating discoveries and treatment benefits to diverse populations. Citation Format: Paula Aristizabal, Arissa MA, Bianca Perdomo, Jesse Nodora, Maria E. Martinez. Racial/ethnic, language, and health literacy disparities on perception of voluntariness during informed consent for pediatric cancer clinical trials [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr A045.