Objective: The present study evaluated the effectiveness of Spirulina mouthwash on the reduction of dental plaque and gingivitis.Methods: A single-blind clinical trial was conducted among thirty patient’s aged 18-40 y visiting dental college and hospital in Bangalore city. Mouthwash was prepared using 0.5% Spirulina. Intervention protocol consisted of instructing the patients to rinse with 10 ml of mouthwash for 1 minute twice daily for 7 d. Plaque index and Gingival index were used to assess the variables at the baseline and after the intervention. The perception of the individual subjects with regard to the use of mouthwash was assessed using 10 cm long visual analog scale (VAS). Statistical analysis was carried out using Wilcoxon signed rank test for mean pre and post plaque and gingival scores respectively. Descriptive statistics was performed for VAS questionnaireResults: The results showed a highly significant difference (p<0.001) between the mean plaque scores at the baseline (2.16±0.34) and at the follow up (1.27±0.46). The mean gingival scores at the baseline (1.86±0.38) and at the follow-up (1.05±0.43) also showed a highly significant difference (p<0.001). Regarding the Visual Analog Scale, the mean values of 5 or greater than suggested the responses to be favourable as the values were reflectedConclusion: The study showed that Spirulina mouthwash resulted in significant reduction in dental plaque and gingivitis. Also, the mouthwash was convenient to use without any adverse effects. Hence, the use of herbal mouth rinses such as Spirulina should be supported.