Background Cancer is a growing public health challenge in low- and middle-income countries, where urbanization, nutritional transition and lifestyle changes contribute to modifiable risk factors. In Mauritania, population-based data on cancer-related nutritional, behavioral and anthropometric risk factors remain limited. Objective To describe the frequency of the main nutritional, behavioral and anthropometric cancer-related risk factors among adults living in the three wilayas of Nouakchott. Methods A cross-sectional study was conducted among 1,000 adults aged 18 years and older in Nouakchott. Data were collected using a standardized questionnaire covering sociodemographic characteristics, dietary habits, physical activity and selected health behaviors. Anthropometric measurements were performed to assess body mass index and abdominal adiposity. Abdominal obesity was defined using sex-specific waist circumference cut-off points recommended by the World Health Organization: [≥] 88 cm in women and [≥] 102 cm in men. Results were presented as frequencies and proportions, with comparisons by sex, age group and wilaya of residence. Results Women represented 52.0% of participants, and 53.5% were aged 18-34 years. Excess body weight was frequent, with 38.6% overweight and 28.0% obese. Abdominal adiposity was also common, with 58.0% having increased or substantially increased waist circumference and 48.3% having an elevated waist-to-hip ratio. Physical inactivity was reported by 64.7% of participants, and 15.7% were current smokers. Dietary exposures included high red meat consumption in 66.8%, daily refined cereal intake in 67.5%, daily sugar-sweetened beverage consumption in 14.9%, and limited daily fresh fruit consumption in 13.8%. Significant differences were observed by sex for anthropometric indicators, by age for selected dietary habits, and by wilaya for physical activity, smoking and selected dietary behaviors. Conclusion This study shows a high frequency of modifiable cancer-related risk factors among adults in Nouakchott, particularly excess body weight, abdominal adiposity, physical inactivity and unfavorable dietary habits. These findings support the need to strengthen primary prevention strategies targeting nutrition, physical activity and tobacco control in Mauritania.