Three new cyclic tetrapeptides (1鈥?b>3) have been isolated from the crude fermentation extract of Onychocola sclerotica. The planar structures of 1鈥?b>3 were elucidated by detailed spectroscopic analyses using one- and two-dimensional NMR experiments and high-resolution mass spectrometry. The absolute configuration of the amino acid residues in each cyclotetrapeptide was established by Marfey鈥檚 method. Compounds 1鈥?b>3 displayed activity as cardiac calcium channel blockers (Cav1.2) but did not inhibit the hERG potassium channel and were not cytotoxic. These peptides are the first secondary metabolites ever reported from fungi of the order Arachnomycetales.