Purpose - The purpose of this paper is to investigate barriers to pro-social behaviour in the form of blood donating using self-determination theory. Design/methodology/approach - Respondents were recruited through intercepts at a major international university and at points within the community in a capital city in Australia. Sampling was conducted over a three-week period resulting in a sample of 617 respondents. Findings - Results show intrinsic motivations positively influence intentions towards blood donation, self- identity, and locus of control. Further, despite positively influencing other factors, external regulation positively influenced amotivation indicating the more likely people feel pressured to donate blood, the less likely they will be motivated to donate blood. Originality/value - This would suggest one way to influence more people to become donors is to place greater focus on the positive emotional feelings they derive from the act of donating blood and the control they have over that donation. Using external regulation strategy which often suggests people "must" or "have-to" donate blood may be limiting blood donation numbers.