The presence of monitoring institutions affects quality and effort of leaders. We investigate the effect of intensified monitoring on the ability and effort of leaders for a sample of forest user groups in Ethiopia, and find experimental and non-experimental evidence of an important trade-off: monitoring increases leaders' effort but lowers their quality in terms of education and experience. This effort–ability trade-off only occurs in the presence of alternative income opportunities (affecting the opportunity cost of time) and only among a subsample of leaders with low prosocial motivation. For our context, we document that the net effect of monitoring on economic outcomes is positive.