Dahlia tubers (Pinnata Cav.) with red flowers are known to have high inulin and fructooligosaccharides (FOS) in their tubers, they also contain various minerals such as Fe and others which are needed by the human body. Therefore, this study was conducted to discuss in vitro determination of Fe levels and Fe bioavailabilities prediction from dahlia tuber syrup. The Fe content in the Dahlia tuber syrup was determined experimentally using the X-Ray Fluorescence Spectrometer (XRF) instrument. The Fe bioavailability of dahlia tuber syrup was predicted based on the standardized inulin and FOS content of dahlia tubers against yacon tubers. The results showed that the Fe content in dahlia tuber syrup was 10,2 ppm. The bioavailability of Fe in dahlia tuber syrup in vitro is predicted to be 69.20% – 94.73%. The prediction of a fairly high Fe bioavailability indicates that dahlia tuber syrup is expected to be quite good in increasing the absorption of Fe in the body which can have health effects, among others, can play a role in improving body metabolism and being able to reduce the risk of anemia due to iron deficiency.