Insect produce wide range of protein and peptides as a first fast defense line against pathogen infection. These agents act in different ways including insect immune system activation or by direct impact on the target tumor cells or viruses. It has been shown that some of the insect peptides suppress viral gene and protein expression, rybosilate DNA, whereas others cause membrane lysis, induce apoptosis or arrest cell cycle. Several of the purified and characterized peptides of insect origin are very promising in treating of serious human diseases like human immunodeficiency virus (HIV), herpex simplex virus (HSV) or leukaemia. However, some obstacles need to be overcome. Cytotoxic activity of peptides, susceptibility to proteases or high cost of production remain still unsolved problems. Reports on the peptides antiviral and antitumour mechanisms are scanty. Thus, in this review we present characteristic, mode of action and potential medical applications of insects origin peptides with the antiviral and antitumour activity.