Biobanks depend on the willingness of people to contribute samples for both research and storage; however, the requirements to perform research on biobanked samples are different than the requirements for their use in organ transplants. The objectives of this study were (1) to characterize public attitudes toward tissue and organ donation for transplantation and biobanking and (2) to identify significant predictors of these attitudes. A cross-sectional study was conducted with a total of 1051 adult subjects, all of whom accompanied their ill relatives to the outpatient clinics at King Abdulaziz Medical City. All subjects were given an interview questionnaire about their previous healthcare experiences and an attitude scale to assess their willingness to participate in organ donation for transplantation or tissue donation for research. A total of 64.7% of all participants reported having a positive attitude toward organ donation, and 68.8% of participants reported having a positive attitude toward biobanking. There was a significant and direct correlation between the attitude score related to organ donation and the attitude score related to tissue donation for research (r = 0.513, P < 0.001). After adjusting for other variables by multiple regression analyses, a positive attitude toward either organ donation or tissue donation for research was significantly more prevalent among females (P < 0.001), those who had previously participated in health-related research (P < 0.001 and P = 0.002, respectively), and those who were aware of organ retention controversies (P = 0.036 and P = 0.001, respectively). Other significant predictors of positive attitudes toward only biobanking were a history of previous blood tests (P = 0.038) and the completion of secondary education (P < 0.001). The attitude of the Saudi public is favorable toward both organ donation and tissue biobanking. Attitudes about the 2 types of donations are related. Previous participation in health-related research and awareness of organ retention controversies are significant predictors of attitudes toward both types of donations.