Abstract-Porphyromonas gingivalis, Bacteriodes spp., Capnocytophaga spp., and Aggregatibacter actinomycetemcomitans are bacteries that cause periodontal disease. Periodontal disease is treated by eliminating pathogen bacteries through scaling and systemic or local antibiotics. One of the local antibiotics that is effective as a periodontal treatment is metronidazole gel. A clinical quasi-experiment was done towards chronic periodontitis patients with pocket depth of 4-6mm using one group pre and post test design, with a split mouth method, one side as experimental group and the other as control. Experimental group with 20 teeth was treated by scaling and 1 ml of 25% metronidazole alginate base topical gel was applied while the reapplication was done in the first week. On the control group, only scaling was done with 20 teeth. All clinical parameters were observed on the first visit. Clinical parameters were reobeserved during the first, second, third and fourth week of visit, while pocket depth and clinical attachment level were reassesed during the fourth week of visit. There was a decrease in plaque index, gingival index, bleeding index, pocket depth and clinical attachment level in the experimental and control group. A decreased in plaque index, pocket depth and clinical attacment level were higher in the experimental group compared to the control group. This difference is statistically significant. No inflamation and bleeding were found in the experimental and control group. There are benefits in the application of 25% metronidazolee alginate base topical gel towards chronic periodontitis patients with pocket depth of 4-6mm.