Cancer is the leading cause of global mortality, resulting in millions of deaths each year. Even a small attenuation in cancer rates through preventive care can have a significant impact. Dietary habits are closely associated with cancer. Unhealthy eating habits may contribute to traditional risk factors and accelerate the progression of cancer. Recent studies have demonstrated the potential of healthy dietary interventions in the prevention and treatment of various cancers, particularly through dietary patterns such as the Mediterranean diet, Dietary Approaches to Stop Hypertension diet, plant-based diet, and ketogenic diet. This review summarizes several studies on the impact of dietary patterns on cancer prognosis and explores the recent findings regarding the mechanisms through which dietary interventions influence cancer progression and prognosis.