Background: C- reactive protein, an acute phase protein, is a biomarker of interest in a number of diseases and is currently used as a marker of disease activity. This study was aimed at analyzing the effect of scaling and root planing on C-reactive protein (CRP) levels in the serum of diabetic patients with chronic periodontitis before and after periodontal therapy.Methods: 15 type 2 diabetes mellitus with chronic periodontits (group 1), 15 medically free and had chronic periodontitis (group II) and 10 systemically healthy subjects who served as controls (group ӀӀӀ) were included in this study. Plaque index, gingival index, probing depth and clinical attachment levels were recorded and blood samples were collected in group1and II at base line and 4 weeks after scaling and root planing. In group ӀӀӀ, blood samples were collected at the initial visit only. Blood samples were quantified for high sensitivity CRP levels using ELISA. Glycated hemoglobin was measured in group І at baseline and 4 weeks after therapy.Results: In the present study, significant reductions in clinical index scores were noted in group Ӏ and II after scaling and root planing. Before treatment, the highest level of high sensitivity C- reactive protein (hs-CRP) was observed in group Ι followed by group ΙΙ and the lowest level was observed in the control group. After scaling and root planing, group Ӏ and IIshowed statistically significant decrease in hs – CRP level after periodontal therapy.Conclusion: Periodontal disease especially in diabetic patients with periodontitis was associated with the elevation in serum CRP levels and non-surgical periodontal therapies bring down the levels of the latter as well as glycated hemoglobin level.