Health crises are events that are out of the capacity of affected communities, which have a range from conflicts and terrorism to emerging infectious diseases and climate change. Health crises not only affect human health, but also they have economic, social, and even political consequences. Cancer prevention has areas, including prophylactic surgery, chemoprevention, immunoprevention, and nutritional interventions. In this chapter, we aim to provide a brief overview of health crises with a focus on some major pandemics, explain different cancer prevention modalities, and evaluate the effects of health crises, in particular pandemics on cancer prevention. In this regard, Scopus, PubMed, and Google Scholar were searched up to January 2022 with terms like “primary prevention,” “secondary prevention,” “tertiary prevention,” “quaternary prevention,” “emergencies,” “pandemics,” “influenza pandemic,” “Zika,” “COVID-19,” “human immunodeficiency virus,” and “Ebola” for potential eligible articles. The findings show that different aspects of cancer prevention and care like diagnosis, surgery, radiotherapy, systemic treatment, and ongoing care have been affected by health crises, especially pandemics. Moreover, the frequency of some risk factors for cancer development such as unhealthy diet and insufficient physical activity were higher during health crises. On the other hand, health crises have some pros, including increasing skills and resilience of healthcare providers, revolutionizing telemedicine and telecommunication, and modifying healthcare systems for service supply in some countries. In conclusion, different factors like the type of health crisis and its scope can affect cancer preventive programs during health crises, which can be in favor or against cancer prevention.