Aim: This study compared the remineralization potential of grape seed extract vs sodium fluoride mouthwash in adult patients with postorthodontic white spot lesions assessed with DIAGNOdent after six months. Methodology: A total of 14 participants with 40 lesions received mouthwashes randomly using either; grape seed extract 15% or sodium fluoride (1000 ppm), the participants were asked to use the mouthwash twice daily. The teeth were evaluated with DIAGNOdent after 1, 3 & 6 months. After 6 months, patient satisfaction was also recorded by using a binary questionnaire. Results: Regarding DIAGNOdent scores, 6 months intergroup comparisons revealed statistically significant differences (P=0.0198) for grape seed extract, and a statistically significant difference between different follow-up periods was found in intragroup comparisons within grape seed extract or sodium fluoride (P=0.0001). Regarding patient satisfaction, after 6 months, there was no statistically significant difference between the two materials (P = 0.5302). Conclusion: Both mouthwashes showed a potential remineralizing effect on post-orthodontic white spot lesions in the early testing periods, while grape seed extract mouthwash has a beneficial influence after 6 months. Clinical Significance: Using grape seed extract as a natural remineralizing agent to treat early enamel carious lesions has the potential to be a viable approach.