Background: Various iron-based products are available that are prescribed in iron deficiency. However, inadequate intake of iron due to the discoloration of teeth and perception of beginning caries has been reported. In contrast, other findings indicate cariostatic property for iron. Regarding the dispersion of the results of studies on the effect of iron on the tooth and its importance, this systematic review, reviewed the effect of iron products on dental caries. Methods: To access the articles in this review, which includes Persian and English articles published up to December 2018, keywords were searched based on the outcome of caries, tooth microhardness and dental discoloration on national and international data basis. Both types of in vitro & in vivo studies related to our topic were selected then necessary Information was extracted from each study and appraised by proper checklists. Results: After removing unrelated articles, 34 articles were evaluated qualitatively, which included 30 RCT studies (13 related to caries, 11 related to microhardness and 10 related to discoloration). In decay group 1 study and microhardness group 2 studies received a low risk of bias score. Conclusion: Studies on iron salt combinations reinforce the cariostatic hypothesis, but about the iron drop, because of various configurations and additives cannot be certainty commented. Of course, showing that some iron drops show a cariostatic effect in the presence of a carious diet. In the field of microhardness, the presence of iron in the cariogenic diet decrease changes in microhardness but the acidic diet, we need more in vivo studies. Also about discoloration well-designed studies especially in human beings are required.