Against the background of failing anti-corruption programmes, this article examines the discourse of the anti-corruption international non-governmental organisation Transparency International (TI), thereby focussing on the organisation's use of the concepts of integrity and ethics. Their meaning and significance is explored by looking at policy measures advocated by TI and particularly at the conception of human nature underlying the organisation's discourse. On the basis of TI documents and interviews with TI staff, the article argues that there is dominance within TI discourse of a mechanistic conception of human nature as rational and self-interested. This leads to an over-emphasis on institutional engineering and the strengthening of oversight and control (to set ‘disincentives’ for corruption), while neglecting the social–moral components of human behaviour as well as the political processes of their generation. This conception of human behaviour makes concepts such as ‘ethics’ mean not much more than ‘rules’, ‘integrity’ mean no more than ‘rule-conforming behaviour’ and ‘prevention’ mean no more than ‘control’. While discussing some of the difficulties involved in addressing morals, the article argues that without reconsidering its conception of human nature, it will be difficult for TI to re-orient and improve its approach. Copyright © 2012 John Wiley & Sons, Ltd.