Mycoparasitic fungi, fungi preying on other fungal species, are prolific producers of volatile and non-volatile secondary metabolites. Several secondary metabolites are produced during mycoparasitism to weaken the host and support attack and parasitism. Further, evidence accumulated that some secondary metabolites also act as communication molecules. Besides their antagonistic activity, several fungal mycoparasites exhibit beneficial effects on plants and some of their secondary metabolites have plant growthpromoting and defense stimulating activities. As many secondary metabolism-associated gene clusters remain silent under standard laboratory conditions, the full variety as well as the underlying biosynthetic pathways employed by fungal mycoparasites for secondary metabolite production still await clarification. Nonetheless, the variety of currently known secondary metabolites and their range of activities is impressive already and they exhibit a great potential for agriculture, pharmacology and other industrial applications.