Findings show that both positive and negative mood may hinder or promote information processing. In two experiments, we show that negative mood impairs transfer effects and learning. In the first experiment, N = 54 participants drawn from a training course for the Swiss Corps of Fortification Guards first learned to solve the three- and four-disk Tower of Hanoi (ToH) problem to mastery level. After mood induction, they were asked to solve one proximal (five-disk ToH) and two distal transfer tasks (the Missionary and Cannibal Problem and the Katona Card Problem). Participants in a negative mood solved the transfer tasks less efficiently. In the second experiment, this result was replicated with a sample of N = 80 participants drawn from a training course for nurses. Additionally, mood affected performance if it was induced before the learning phase; participants in a negative mood needed more repetitions to reach the mastery level and also performed worse in the transfer tasks, although there were no greater mood differences in this problem-solving phase. The implications for the design of learning settings are discussed.