Emerging and re-emerging diseases are on rising trend and have been threats to humans till date. Most of the emerging and re-emerging diseases noted since past three decades are of zoonotic nature, particularly of viral origin. The effects of these diseases have recently been emphasized by notable outbreaks as of those involving SARS-Cov2 (COVID-19), Nipah, Avian Influenza (H5N1), Swine Influenza (H1N1), West-Nile Fever, Ebola, Zika etc. Emergence of the above diseases whose nature of occurrence is unexpected and re-emergence of unusual outbreaks of diseases like leptospirosis, brucellosis, rabies, plague, antimicrobial resistance etc., pose marked effects on national economies, human and animal health. Eventhough the exact reasons for the emergence of emerging and re-emerging zoonoses are not clear, there are many factors which are thought to be involved for their occurrence. These factors are complex in nature and categorized into factors of infectious origin (virus, bacteria, and prion), human and ecological factors. This article gives an insight about understanding the role of factors and measures for controlling their emergence.