Chlorhexidine (CHX) is an effective antibacterial agent and is used in dental treatment in several formulations. The aim of this study was to compare the effectiveness of CHX solution and CHX gel on dental plaque inhibition and gingivitis relief by a randomized clinical trial. Thirty-eight participants were randomly divided into two groups: control group (0.12% CHX solution) and test group (1% CHX gel). Participants were provided with CHX products and were instructed to use each product in the morning and evening for 1 week. Clinical results were evaluated by analyzing the collected data of Turesky et al. the modified Quigley-Hein Plaque Index (TQHPI), gingival index (GI) and the BANA test. Measurements were conducted 4 weeks and 8 weeks after using chlorhexidine products. The results were analyzed using repeated measured ANOVA and paired t-test. TQHPI and GI were significantly different after treatments in both groups (p < 0.001). The GI decreased more in the test group compared to the control group 4 weeks and 8 weeks later. In both groups, the BANA score also significantly decreased (p < 0.001) after 8 weeks, though the BANA score decreased relatively more in the CHX gel group than the CHX solution group. These results suggest that 1% CHX gel is more effective in reducing gingivitis and bacteria of periodontal disease than the 0.12% CHX solution. Therefore, the 1% CHX gel is expected to be actively used for non-surgical treatment of periodontal disease patients.