Background: Periodontitis is a chronic inflammatory disease that affects the teeth’s supporting structures, leading to clinical attachment loss, pocket formation, and tooth loss if left untreated. Scaling and root planning (SRP) is the gold standard for removing bacterial biofilm and calculus from tooth surfaces. However, in most situations, including tooth fractures, there is a need for adjunctive therapies to complement and improve treatment outcomes. This study aimed to evaluate the efficacy of locally delivered metformin (MF) 1% gel as an adjunct to SRP in treating severe chronic periodontitis. Materials and Methods: A total of 36 volunteers were randomly assigned to two treatment groups, namely, SRP plus placebo gel and SRP plus 1% MF gel. Clinical parameters such as pocket probing depth (PD), clinical attachment level (CAL), and gingival recession (GR) were recorded at baseline, 2, and 4 months. The data were analyzed using independent T-tests, one-way, and repeated measures analysis of variance (ANOVA) using SPSS 24 software. Results: All groups exhibited improvements in periodontal parameters such as PD and CAL. While the mean reductions in PD and CAL were not statistically significant after 3 weeks of treatment between the two groups (P=0.193), the MF group demonstrated significantly greater improvements in PD, measuring 3.49 mm compared to 1.87 mm in the control group (P=0.007), as well as in CAL, which measured 2.98 mm versus 1.72 mm in the control group (P=0.014). Conclusion: The adjunctive use of locally delivered 1% MF gel could stimulate a significant reduction in PD and increases in CAL compared to the placebo gel, while there was no GR resulting from the local delivery of the drug. This suggests that the MF gel may offer benefits in the treatment of severe chronic periodontitis by enhancing periodontal healing without inducing GR.