Objective: The current in vitro study was performed to evaluate the effect of fluoridated mouthwashes and immersion time on the corrosion behavior and microscopical surface of two different types of orthodontic mini-implants (titanium (Ti) and stainless steel (SS)). Methods: Total 30 orthodontic mini-implants (15 titanium and 15 stainless steel) were collected. Each group was subdivided equally into 3 subgroups which were immersed separately in (Artificial saliva, Lacalut-white and Kin B5 mouthwashes) for 28 days at following immersion intervals: 1-7 days, 8-14 days and 15- 28 days. All mini-implants were assessed for metal ions release, however, only 6 MIs: 3 Ti and 3 SS were selected from the studied groups (one from each group), and subjected to SEM analysis before and after immersion in the storage media. The mini-implants were used in as received condition without any additional treatment. Results: The results of (SEM) showed that the pitting and crevice corrosion was obvious in different regions of examined samples, being greater in titanium than stainless steel mini-implants, and more evident in both fluoridated mouthwashes than artificial saliva. Conclusion: The results of the microscopical examination revealed that the signs of corrosion in the form of crevice and pitting were detected in all groups of MIs, being most evident in those immersed in fluoridated Kin-B5 MW followed by fluoridated Lacalut-White MW and finally the artificial saliva group.