BACKGROUND: With the coronavirus disease 2019 (COVID-19) pandemic continuing to accelerate and blood collection agencies (BCAs) warning of shortages, it is critical to identify the current determinants of donor behavior for donors and nondonors. STUDY DESIGN AND METHODS: In May and June 2020, Australian residents who believed themselves eligible to donate blood responded to measures assessing constructs from an integrated protection motivation theory, organizational trust, and theory of planned behavior framework, with donor status also assessed. RESULTS: A total of 507 residents (47% male, mean age 28.69 years; 272 had donated/attempted to donate) participated. A revised structural equation model was a good fit to these data. In this model, perceived risk, severity, anxiety, and response cost associated with donating during the COVID-19 pandemic underpinned threat appraisals, while response efficacy, self-efficacy, and attitude toward donating during COVID-19 informed coping appraisals. Trust in the BCA predicted lower threat and higher coping appraisals, and higher coping appraisals predicted stronger subjective norms. Intention to donate during the COVID-19 pandemic was positively predicted by subjective norm and self-efficacy. Donation-related behavior was positively predicted by intention, with this relationship stronger for nondonors than donors. CONCLUSION: Self-efficacy and approval from others, underpinned by coping appraisals and organizational trust, play a critical role in intentions to donate. BCAs that focus on maintaining trust with (potential) donors, providing clear messaging stating the minimal threat of contracting COVID-19 from donating and the protective measures in place, and showing how donating is achievable, may help to ensure a safe and secure blood supply throughout the COVID-19 pandemic.