Background. Informed consent is a key ethical requirement for biomedical research that is implemented to ensure autonomy and voluntary participation. However, patients in the intensive care unit (ICU) may be unconscious or severely ill and thus lack the capacity for decisions about research participation. Thus, relatives or guardians are usually asked to provide informed consent prior to the inclusion of ICU patients in research. Aims. This study aimed to assess the attitudes and preferences of relatives of ICU patients toward informed consent in biomedical research in Jordan. Subjects and Methods. A sample of 184 relatives with a critically ill next of kin in the ICU was anonymously surveyed regarding their attitudes and preferences toward giving informed consent for biomedical research on behalf of their patients. Results. The study showed that the majority of relatives had a positive attitude toward the informed consent process on behalf of their patients in the ICU (72.3%). The perception that participation in research would be directly beneficial to their patient was the most significant reason to provide informed consent among relatives. The degree of relatedness to the patient was significantly associated with the decision to provide informed consent on behalf of the patients in the ICU. Additionally, more than 70% of the relatives strongly agreed to take part in clinical research if they were to be unconscious patients in the ICU. Moreover, the majority of the respondents agreed that their first-degree relatives would give consent on their behalf. Conclusion. Relatives with a critically ill next of kin in the ICU had positive attitudes toward providing informed consent on behalf of their patients. This was motivated by the direct benefit from the research to their patient.