Powdered soft drinks are instant, cheap and have high yield (1 liter per each 25 g-package), which justifies their consumption among different social classes in Brazil and European countries such as England, Turkey and Hungary. Some of these drinks are voluntarily enriched with iron, and are included in the Brazilian monthly basic grocery package. The World Health Organization reports that more than 2 billion people are iron-deficient worldwide. Therefore, it is worth to assess the iron content in the samples by a simple validated and adequate method. Thus, this study developed and validated a simple and cheap method by wet ashing and Flame Atomic Absorption Spectrometry (FAAS) to determine the iron content in these powdered soft drinks, validated based on AOAC (2012) and MAPA (2011) guides. For the method validation, three iron-containing and one zinc-containing brands of powdered soft drinks, in grape and passion fruit flavors, were collected in the market of Campinas, SP, Brazil. This study validated the parameters of linearity (R²=0.99), limit of detection (0.033 mg/L), limit of quantification (0.110 mg/L), accuracy (between 102.77 and 111.68%), precision within and inter-days (p-valor <0.05 and F calculated < critical F), and ruggedness through a 2(4-1) design of experiment with three center points, according to Rodrigues & Iemma (2014), to evaluate the effect of varying the sample mass, volumes of hydrogen peroxide and nitric acid and the temperature for sample mineralization at 95% of confidence level. These parameters corresponded to the required by the guides, and the method was considered linear, precise, reproducible, accurate and robust. Once this method is valid, it provides a reliable determination of iron in grape and passion fruit powdered soft drinks for their quality control in the industrial production line, for example.