Milk and dairy products are a source of numerous compounds exhibiting scientifically proven bio- logical activity, including proteins, such as immunoglobulins, lactoferrin, lactoperoxidase and lysozyme. This activity is multifaceted, with antimicrobial (antibacterial, antiviral and antifungal) and immunomodulatory effects. The content of these proteins in the diet is one of the factors determining a normal immune response. Therefore, the aim of the study was to review the literature on this subject and present these properties. Lactoferrin has been found to be the milk protein exhibiting the highest antiviral activity. By binding and sequestering iron, it removes this element from the growth environ- ment of microorganisms. Clinical trials have shown it to be effective in inhibiting infection with the hepatitis B and C viruses (HBV and HCV), herpes simplex virus 1 and 2, human immunodeficiency virus (HIV), human cytomegalovirus, human papilloma virus (HPV), enteroviruses, adenoviruses, influenza viruses, parainfluenza viruses, and rotaviruses, the most important aetiological agent of acute diarrhoeal disease, which is one of the major causes of mortality in infants and young children in developing countries. Furthermore, it has been found to act synergistically with antiviral drugs, including interferon, acyclovir and cidofovir, allowing the doses of drugs with high toxicity to be re- duced. Moreover, peptides derived from lactoferrin, such as lactoferrampin and lactoferricin, are used in medicine as protection against viruses. The use of immunoglobulin-based supplements has also been shown to reduce the incidence of diarrhoea induced by rotaviruses in infants and children up to four years of age. In addition, lactoperoxidase inactivates HIV 1 and poliovirus. Recent years have seen a rapid increase in the number of viral infections, which of course is due to the virus SARS- CoV-2. It has been demonstrated that the immunopathology associated with the virus may be inhib- ited by certain milk proteins and probiotic strains of Lactobacillus and Bifidobacterium. Trials by the New Zealand pharmaceutical manufacturer Quantec showed that a protein complex containing lacto- ferrin and lactoperoxidase, obtained from fresh pasteurized cow milk, may protect human cells against COVID-19. The patented defence protein IDP exhibits anti-inflammatory, antioxidant and antimicro- bial activity. To conclude, the content of these antiviral proteins in milk and dairy products was as- sessed in the study. Milk and dairy products are readily available, and the scientifically proven proper- ties of milk proteins should encourage their inclusion in the diet.