The present study was conducted to investigate the concentration of nitrate in drinking water resources and its carcinogenic risk in the southern provinces of Iran in 2020. Raw data of nitrate concentrations were obtained from wastewater and water Company of each province, and Mont Carlo Simulation (MCS) was considered 10‐5 for estimating human carcinogenic risk. Our results demonstrated that in the drinking water resources of Khuzestan and Fars provinces, the nitrate level was 59 and 72 mg/L, respectively, higher than the World Health Organization (WHO) recommendation. The calculated carcinogenic risk of nitrate for Khuzestan and Fars provinces were higher than the range set by WHO and Health Canada, 8.8 × 10−5 and 1.3 × 10−5, respectively. Exposure to an unacceptable nitrate level through drinking water can affect blood carrying oxygen and cause methemoglobinemia and a significant relationship with gastrointestinal cancer spread. [ABSTRACT FROM AUTHOR]