Machiavellianism is typically considered to encompass rather negatively connoted characteristics such as being ruthless, deceitful or self-centred. Concerning its influence on job performance, there have been notions about a positive linear association as well as a negative one. Somewhat reflecting these different views, a recent meta-analysis regarding this link indicated both large variability in respective empirical investigations and no substantial linear association. Herein, we aimed to integrate the theoretical underpinnings of both perspectives of a linear link by proposing an inverted U-shaped relation between Machiavellianism and job performance. Using data from n=235 dyads of self-rating and colleague rating, results supported this hypothesis with regard to the three dimensions of organisational citizenship behaviour, whereas no support was found with regard to task performance. More precisely, intermediate levels of Machiavellianism yielded the highest organisational citizenship behaviour as compared with both lower and higher levels-although employees with lower levels had outcomes nearly as high as those of employees with intermediate levels. Further, tenure was found to moderate the curvilinear relation between Machiavellianism and organisational citizenship behaviour directed at individuals. In sum, this investigation might help to disentangle different understandings of the effects of Machiavellianism in organisational life and beyond.