The effect of nutrition in the development and prognosis of cancer has received a lot of attention. Research shows taking vitamins, which are powerful antioxidants, can significantly lower the risk of cancers. Nutritional supplements suited to a patient's background, genetics, diet, tumour histology, and therapy may be beneficial in some cases. A poor diet may have a negative impact on immunity and treatment tolerance, decreasing the efficacy of chemotherapy in destroying malignant cells. Most cancer patients now take vitamins to supplement regular treatment and/or to decrease side effects from the medicine as well as the underlying ailment. This is a new development in recent decades, whereas taking nutritional supplements while receiving cancer treatment may increase the success of chemotherapy. To enhance the quality of life, lengthen the survival rate, and sustain immunotherapy compliance, additional study into the use of micronutrients in medical treatment is required for cancer patients. The main purpose of this book chapter was to highlight the role of vitamins in cancer and to establish a solid foundation for future research on this exciting topic. The possible impact of some vitamins in various malignancies such as colorectal, breast, prostate, lung, pancreatic, and stomach cancers are investigated.