The present study investigated the influence of mood state (positive vs. negative) on the cognitive control process of conflict adaptation. A task-switching paradigm was applied, allowing to assess conflict adaptation both within tasks and across tasks. A success-failure manipulation was applied for mood induction. Within-task conflict adaptation tended to be larger in negative mood than in positive mood, in line with previous findings in the literature. Across-task conflict adaptation was also observed, but only in the positive mood group: Participants in positive mood showed larger conflict adaptation than participants in negative mood. We suggest that different cognitive mechanisms underlie this double dissociation: Within-task conflict adaptation is enhanced in negative mood because response conflict is aversive in nature, and is therefore congruent to negative mood states. Between-task conflict adaptation is only present in positive mood because of less distinct task representations under positive mood, leading conflict adaptation to transfer to the other task. The data show that influences of mood state on cognitive control are multifaceted, with some control processes being enhanced and others attenuated in negative relative to positive mood.