Cancer is a broad term for a group of diseases that begin when abnormal cells grow out of control in practically any organ or tissue of the body. A variety of nutrients are included in the diet of people with cancer but omega-3 polyunsaturated fatty acids are one of the most effective nutrients. Numerous clinical and epidemiological studies have shown that polyunsaturated omega-3 fatty acids play an important role in maintaining the health of people with cancer. Omega-3 polyunsaturated fatty acid, by their own antioxidant, antitumour, anticarcinogenic, and neuroprotective properties, help cancer patients to reduce their various physical complications. Fish oil contains omega-3 fatty acids mainly docosahexaenoic acid and eicosapentaenoic acid have antioxidant properties that help to increase antioxidant enzymes and remove the reactive oxygen species from cancer patient’s body and also reduce the oxidative stress. Now, omega-3 polyunsaturated fatty acid is considered as pharmaconutrient. As a pharmaconutrient, omega-3 fatty acid reduces the inflammatory response of cancer patients. The cyclooxygenase-2 expression is suppressed by the omega-3 fatty acid and reduce the growth of tumour cell. Mental wellness is a significant lifestyle aspect that the cancer patient cannot maintain. As a result, they are suffering from major depression. Omega-3 fatty acids exhibit neuroprotective activity against various brain diseases. This review summarizes that the omega-3 polyunsaturated fatty acids have an antioxidant and anticarcinogenic function that can inhibit the cancer cell growth and maintain the health status and lifestyle behaviour of the cancer patients.