Purpose: To evaluate in a systematic review whether the use of dental floss in primary teeth is associated with a reduction in incidence of proximal caries. Materials and Methods: Searches were performed using the following databases: PubMed MEDLINE, Web of Science, Bireme, Scopus and The Cochrane Library. Only 5 studies were eligible for inclusion. The quality assessment and bias control of the studies were carried out based on the Fowkes and Fulton Guideline. The study concept was first registered in the international prospective register of systematic reviews (PROSPERO). Results: Flossing was professionally performed in one study and self-reported (by parents or by the children) through questionnaires in all other 4 studies. In the first study, the authors concluded that daily interdental flossing resulted in a significant reduction in the incidence of proximal caries in deciduous teeth during a 20-month period. Two cross-sectional studies found that the use of interdental floss did not show any relevant association with the prevalence of caries; one study found that a higher the frequency of flossing was associated with higher caries experience, and the other found an association between severe caries and the use of dental floss, independently of the flossing frequency. Conclusion: There is only one study in the current literature showing evidence of an association between the use of dental floss and proximal caries reduction on primary dentition. However, the use of dental floss should never be discouraged. Healthy habits acquired in childhood continue throughout adult life, with numerous oral- and general-health benefits. Keywords: deciduous, dental caries, dental devices, home care, proximal caries, tooth