How does negative mood affect risk taking? A brief questionnaire was used to measure state anxiety, depression, and fatigue, and a daily mood diary allowed state and trait (average level) mood to be separated. Studies 1 and 2 used natural moods and Study 3 a mood induction procedure. Risk was assessed using hypothetical everyday choice scenarios. Study 1 showed that riskiness was affected by state fatigue, but not by anxiety and depression. Study 2 showed that increased riskiness over a two-week period was predicted by fatigue changes, after controlling for riskiness and trait and state mood at time 1. Fatigue effects were stronger for more important scenarios, and when state anxiety was also high. In Study 3, covariance analyses showed that the observed increased in riskiness was related to induced fatigue, rather than to anxiety or depression. The effects are discussed in relation to the literature on fatigue effects, and models of mood and cognition.