A series of peptides derived from three domains within the fusion protein of Sendai virus was synthesized and examined for their potential to inhibit the fusion of the virus with human red blood cells. These domains include the ‘fusion peptide’ and two heptad repeats, one adjacent to the fusion peptide (SV‐163) and the other to the transmembrane domain (SV‐473). Of all the peptides tested, only SV‐473 was highly inhibitive. Using fluorescently‐labelled peptides, the mechanism through which the SV‐473 peptide inhibits the haemolytic activity of the virus was investigated. The results suggest that interactions of the active peptide with virion elements and lipid membranes are involved. Since it has recently been found that synthetic peptides corresponding to putative coiled‐coil domains of the human immunodeficiency virus (HIV) type 1 transmembrane protein gp41 are potent inhibitors of HIV, we discuss the general property of virus‐derived coiled‐coil peptides as inhibitors of viral infection.