Objective: Chronic fluoride poisoning is called fluorosis. The aim of the study was to investigate effects of fluorosis on cardiovascular system in children by measuring QT dispersion (QTd), corrected QT dispersion (QTcd), heart rate variability (HRV) and echocardiography findings. Materials and Methods: Thirty-five children with dental fluorosis and 26 children as control group were included in this cross-sectional study. Dean index was used for the clinical diagnosis. The fluoride levels of subjects measured by ion electrode method in spot urine higher than 0.6 ppm were included in the study. Serum electrolytes and thyroid function tests were analyzed. Electrocardiography (ECG), echocardiography and 24-hour ambulatory Holter monitorizations were applied, and all the data were analyzed for measuring HRV, and calculation of QTd and QTcd intervals. Corrected QT (QTc) intervals were determined with the Bazzett formula. Difference between the longest and shortest intervals was considered as dispersion. Statistical analysis was performed Kruskal-Wallis test and Pearson correlation test. Results: Low free thyroxine hormone (FT4) (Control Group, Group 2 1.11 (0.85-1.64) ng/dL, 0.96 (0.85-1.11) ng/dL, p<0.05), calcium (Control Group, Group 1, 2, 9.80 (9.30-10.70) mg/dL, 9.60 (8.90-10.70) mg/dL, 9.50 (8.90-10.10) mg/dL, p<0.05) and high serum sodium levels (Control Group, Group 2 139 (136-142) mEq/L, 141 (138-148) mEq/L, p<0.01), increased QT (Control Group, Group 2 329.8 (300.0-363.5) msec, 351.8 (318.0-372.0) msec, p<0.05) and QTc intervals (Control Group, Group I2 390.6 (309.0-418.5) msec, 366.8 (318.2-468.5) msec, p<0.05) were found in subjects with fluorosis. No significant difference was found with respect to echocardiography and HRV variables. Conclusion: Endemic fluorosis is a risk factor for decrease in calcium and FT4 levels, increase in sodium levels and QT prolongation. These findings might be related with some cardiovascular system dysfunctions such as arrhythmias or syncope. Subjects with fluorosis should be monitored in terms of long QT and QTc intervals.