Organ donation intentions and behaviors were investigated using a traditional and extended theory of planned behavior (TPB). In study 1, attitudes, subjective norms, and perceived behavioral control were associated with intentions to engage in donation behaviors in a student sample (all p ≤ .02), and intentions significantly predicted behavior 2 months later (p < .001). Study 2 utilized a community sample of Catholic, Jewish, and Muslim individuals. Measures of affect and religious attitudes were added to the traditional TPB, increasing the variance in intentions accounted for by the model, F(7, 181) = 6.94, p < .001. The studies support the use of an extended TPB in predicting donation-related intentions and behaviors and suggest potential targets of interventions to promote donation.