Background Dietary supplements (DSs) are not recommended for the prevention of cancer recurrence. Although DS use is common in individuals living with and beyond cancer, its associations with beliefs about reduced cancer recurrence risk and demographic and health behaviors are unclear. Methods Adults (18 years old or older) who had been diagnosed with breast, prostate, or colorectal cancer were recruited through National Health Service sites in Essex and London. Participants completed a mailed survey and telephone or online 24‐hour dietary recalls (MyFood24). Supplement use was collected during the dietary recalls. Associations between DS use and demographics, health behaviors, and beliefs about DSs and cancer were explored. Results Nineteen percent of 1049 individuals believed that DSs were important for the reduction of cancer recurrence risk, and 40% of individuals reported DS use. DS use was positively associated with being female (odds ratio [OR], 2.48; confidence interval [CI], 1.72‐3.56), meeting 5‐a‐day fruit and vegetable recommendations (OR, 1.36; CI, 1.02‐1.82), and believing that DSs were important for reducing cancer recurrence risk (OR, 3.13; CI, 2.35‐4.18). DS use was negatively associated with having obesity (OR, 0.58; CI, 0.38‐0.87). The most commonly taken DSs overall were fish oils (taken by 13%). Calcium with or without vitamin D was the most common DS taken by individuals with breast cancer (15%). Conclusions DS use by individuals living with and beyond cancer is associated with demographic factors and health behaviors. A belief that DSs reduce the risk of cancer recurrence is common and positively associated with DS use. There is a need for health care professionals to provide advice about DS use and cancer recurrence risk.