The tendency to experience negative emotions in the face of stress may lead to repeated overactivation of the hypothalamic-pituitary-adrenal axis. In a sample of 556 women, this study used the Experience Sampling Method to assess different daily stressors, current mood, and salivary cortisol, 10 times daily for 5 days. Multilevel analyses estimated the contributions of stressors and mood states as predictors of salivary cortisol secretion. Results showed that minor stressors were associated with decreased positive affect and increased negative affect, agitation, and cortisol. Of the mood states, only negative affect was independently associated with cortisol. Negative affect also mediated effects of daily stressors on cortisol. Although further research is needed to clarify: (i) the causal pathways between daily stress, mood, and cortisol and (ii) the importance of daily stress reactivity as a prospective risk factor, these findings confirm that minor daily stressors can influence emotional and biological processes involved in subjective well-being.