Background Periodontal disease may be associated with more bacteria and consequent induction of a systemic inflammatory process, with changes in the levels of C-reactive protein (CRP). The purpose of this cross-sectional study was to evaluate the association between periodontitis and serum levels of C-reactive protein. Material and Methods The sample comprised 100 individuals distributed into two groups according to serum levels of C-reactive protein: normal or altered. Social, biological and behavioral data were collected by means of a structured questionnaire. Additionally, a blood test was requested to measure C-reactive protein levels. CRP values less than 3 mg/l were considered normal. Periodontal clinical examination was conducted in each participant for analysis of probing depth, bleeding on probing and clinical attachment level. Descriptive statistics, univariate analysis and logistic regression were performed. Results were provided in odds ratio, confidence intervals and p values. Results Individuals with altered C-reactive protein levels showed a higher prevalence of periodontitis than individuals with normal C-reactive protein levels ( p =0.008). In the final logistic regression model, individuals with periodontitis were more likely to present altered C-reactive protein than individuals without periodontitis (OR=3.27, CI=1.42-7.52, p =0.005). Conclusions The alteration of the C-reactive protein levels among individuals with a higher prevalence of periodontitis corroborates clinical evidence that periodontal infection has a systemic impact. Key words: C-reactive protein, cytokines, periodontal diseases, periodontitis.