To reduce anemia among adolescent girls, factors that influence the consumption of iron-rich foods/IRF have not been investigated, and neither has a tool been developed to assess its determinants. Using the extended version of the theory of planned behaviour/eTPB, this study aims to develop and validate a questionnaire assessing individual and environmental factors that could influence IRF intake among Senegalese adolescent girls aged 10–19 years old. First, eight focus group discussions (FGDs) were held in different regions to identify salient beliefs related to each of the four constructs of the eTPB. Information from FGDs was used to develop a questionnaire that was administered to the first group (n = 200) of girls. Principal component and exploratory factorial analyses were then performed to identify latent factors for each construct. A modified version of the tool was administered to the second sample of girls (n = 400), and confirmatory factorial analyses were conducted. Hancock and Muller’s H reliability index was computed on the final model. Most metrics for fit indices were respected, and the H value was satisfactory. This study proposes a tool that could be used to explore determinants of the consumption of IRF among adolescent girls.