The aim of this study was to evaluate HRV in children requiring intensive care unit stays due to TCA poisoning between March 2009 and July 2010. In the time- domain nonspectral evaluation, the SDNN(P < 0.001), SDNNi (P < 0.05), RMSDD(P < 0.01), and pNN50 (P < 0.01) were found to be significantly lower in the TCA intoxication group. The spectral analysis of the data recorded during the first 5 minutes after intensive care unit admission showed that the values of the nLF (P < 0.05) and the LF/HF ratio (P = 0.001) were significantly higher in the TCA intoxication group, while the nHF (P = 0.001) values were significantly lower. The frequency-domain spectral analysis of the data recorded during the last 5 minutes showed a lower nHF (P = 0.001) in the TCA intoxication group than in the controls, and the LF/HF ratio was significantly higher (P < 0.05) in the intoxication group. The LF/HF ratio was higher in the seven children with seizures (P < 0.001). These findings provided us with a starting point for the value of HRV analysis in determining the risk of arrhythmia and convulsion in TCA poisoning patients. HRV can be used as a noninvasive testing method in determining the treatment and prognosis of TCA poisoning patients.