Fish is well known for its nutritional value rich in high-quality protein, omega-3 fatty acids, vitamins, and minerals, which may lower cancer risk. However, it can also contain harmful heavy metals and contaminants or be preserved with salt, posing health risks, particularly to vulnerable populations. Evidence from previous epidemiological studies suggests that overall, the association between fish consumption and cancer risk may vary by cancer sites. Fish intake is associated with either lower risk or no significant association with breast, colorectal, gastric, bladder, lung, pancreatic, esophageal, liver, and prostate cancers, and it may be beneficial in reducing cancer mortality. However, fish intake is potentially associated with a higher risk of nasopharyngeal carcinoma and melanoma. Recently, some Mendelian randomization studies have been conducted to support the causal relationship between higher fish intake and reduced breast, colorectal, and lung cancer risk. To reduce health risks and maximize the benefits of fish intake, it is advisable to limit consumption of fish with higher concentrations of heavy metals, such as larger, predatory, and longer-lived species. The health impact of fish may also depend on preparation and cooking methods. Limiting intake of salted fish can be beneficial as well. Additionally, local governments should regularly monitor metals and contaminants in water, sediment, and fish to ensure consumer safety.