Previous literature demonstrates that people’s beliefs about the determinants of income inequality play a major role in the decision whether to support income redistribution. However, not much is known about how people form these beliefs and the degree to which self-serving biases influence their formation. This study investigates whether people form self-serving beliefs regarding the extent to which work versus luck determined their income, and particularly whether such beliefs are driven by the desire to support personally advantageous redistributive policies. To address this question, I conduct a laboratory experiment that exogenously varies participants’ incentive to distort their beliefs. I find that participants attribute income inequality to work when they are rich, and to luck when poor, but the financial incentive of benefitting from an advantageous redistributive policy does not make this effect any stronger. I also measure preferences over redistributive policies, and confirm that these are influenced by the elicited beliefs.