This study aimed to evaluate the possible association between periodontitis and systemic complications in a Brazilian type 1 diabetes population. A multicentre, sectional study was carried out in 28 public clinics located in 20 Brazilian cities. Data from 3,591 patients were obtained (56.0% females, 57.2% Caucasians), with an average age of 21.2 ± 11.7 years and whose mean duration of type 1 diabetes was 9.6 ± 8.1 years. Periodontitis was evaluated through self-report. Odds ratios (OR) and 95% confidence intervals were calculated to evaluate the association between periodontitis and systemic diabetes complications (chronic micro and macrovascular complications and hospitalizations by hyperglycemia and diabetic ketoacidosis). The prevalence of periodontitis was 4.7% (n=170). Periodontitis patients had mean age of 27.4 ± 12.9. This group was older (p<0.001), exhibited longer diabetes duration (p<0.0001) and had elevated total cholesterol (p<0.05), triglycerides (p<0.001) and lower HDL (p<0.05) values than patients without periodontitis. Systolic and diastolic blood pressures were significantly increased in periodontitis patients (p<0.01). Periodontitis patients had increased odds of microvascular complications (2.43 [1.74-3.40]) and of hospitalizations related to hyperglycemia (2.76 [1.72-4.42]) and ketoacidosis (2.72 [1.53-4.80]). In conclusion, periodontitis was associated to systemic complications in Brazilian type 1 diabetes patients.