The study aims to assess the general population’s knowledge and practice of basic nutrition, food safety, and hygiene in rural, urban and slum areas of Bangladesh. To obtain nationally representative information on issues related to basic nutrition, food safety and hygiene related knowledge and practice; a survey was conducted in rural, urban and slum areas of all eight divisions of the country, where a cross-sectional study design was followed. Data was collected from four types of respondents, namely, food purchasers, cooks, adolescents and caregivers from 5,000 households situated across the country. Results show that overall, one-third of the respondents living in rural-urban areas and two-fifths in slums had a low basic nutrition knowledge including absence of knowledge on foods rich in vitamin A and Iron; lack of knowledge on adverse health effects of trans-fatty acid, such as, cardiovascular disease risk; low knowledge on adverse health effects of unfavorable nutrition behavior (e.g. eating salty/savory foods—puri, singara, crisps and chips, chanachur, etc; sweet foods/sugary foods; sugar sweetened beverages); lack of knowledge about adequate dietary diversity from consuming a variety of foods and well-balanced diet; the lowest knowledge of basic nutrition and adverse health effects of unfavorable nutrition behavior compared to other types of consumers in the case of adolescents living in urban areas. Consequently, overall, 43 percent of cooks living in rural-urban and slum areas had low knowledge on cooking best practices, including, most of the cooks (74.5 percent) did not mention that vegetables need to be cleaned before cooking, fifty seven percent of cooks did not know how many times cooked food is safe to reheat before consumption.