Background: Studies in the West have demonstrated that appropriate informational support is a vital component of cancer care, with positive effects on both patients and their informal caregivers. Since little is known about the information needs of advanced cancer patients and informal caregivers in China, where ‘silence as virtue’ is much more valued and the communication style is less open, this study was therefore conducted to elaborate the information needs of advanced cancer patients and informal caregivers as well as to explore their perceptions and experiences regarding their unmet information needs in the Chinese context. Methods: This sub-study of a previous cross-sectional survey utilized a qualitative descriptive study design. The approach involved semi-structured interviews that followed an interview guide to collect data. Eligible participants were the advanced cancer patients and informal caregivers who had participated in the previous cross-sectional survey and reported unmet information needs. Each interview was audio-recorded and transcribed verbatim. Descriptive content analysis was used to analyze the data. Results: Seventeen advanced cancer patients and 15 informal caregivers with unmet information needs participated in the semi-structured interviews, with ages ranging from 32 to 63 years old for patients and from 32 to 70 for informal caregivers. Four categories were extracted from the interviews with the patients and caregivers: (1) types of unmet information needs; (2) reasons for information needs not being met; (3) preferences for the provision of information; and (4) meaning and role of information. Each category had two to four sub-categories for both the patients and the caregivers, which were similar but not completely the same. Conclusion: The findings indicated that the provision of appropriate information could promote informed decision-making and greater satisfaction with treatment options, reductions in psychological disturbances, and enhanced confidence and ability in self-management and capacity in caregiving. Moreover, information on Traditional Chinese Medicine and food therapy should be increased, particularly for patients at the follow-up stage, while the amount of information on prognosis should be flexible as it could increase patients’ and caregivers’ psychological burden. Healthcare professionals were the most preferred information provider, although their heavy workload resulted in time constraints. In this case, they should provide information to patients and caregivers together as a ‘whole unit.’ At the same time, the value of separate conversations should also be recognized as some caregivers preferred to conceal unpleasant information from the patient.