Post-Traumatic Stress Disorder (PTSD) is a psychological disorder resulting from direct or indirect exposure to severe stressful and traumatic events. Among the various methods for investigating brain activity, electroencephalography (EEG) has emerged as an important non-invasive approach for examining brain electrical activity, particularly in the context of PTSD. In recent years, analysis of EEG signals using the Autocorrelation Window (ACW) has gained attention for examining the intrinsic neural timescales of brain activity. In this study, two metrics, ACW-0 and ACW-50, were extracted and analyzed to evaluate the intrinsic neural timescales of the brain activity in healthy individuals and patients with PTSD. In addition, the mean values of these indices were computed for each channel, and between-group differences were examined on a channel-by-channel basis. The results showed that although no significant difference was observed in the overall mean ACW-0 between the two groups, ACW-50 was significantly reduced in individuals with PTSD compared to healthy individuals and exhibited a large effect size. In the channel-by-channel analysis, some channels showed differences between the two groups in the initial analysis; however, after applying the Benjamini–Hochberg correction for multiple comparisons, none of these channel-wise differences remained significant at the q < 0.05 level. These findings suggest that ACW-50 may be considered a promising feature for investigating alterations in the timescale of brain activity associated with PTSD.