When it comes to simultaneous processing of two tasks, information processing capacity is usually below par and not desirable. Therefore, this preliminary study aimed to investigate the effect of transcranial direct-current stimulation (tDCS) of dorsolateral prefrontal cortex (DLPFC) on performing dual tasks. Twenty-six students (average age 25.2 ± 2.43 years) were selected and then randomly divided into experimental and sham groups. All of the participants conducted the Stroop effect test in a dual task situation before and after the tDCS. This test included two intervals between the stimuli of 100 and 900 ms. The results of mixed-ANOVA showed that the average second reaction time of the experimental stimulated group was reduced (in both dual tasks with congruent and incongruent stimuli) significantly after the tDCS. Therefore, it can be stated that the tDCS of the DLPFC increases the information processing speed and the capacity of attention and, as a result, decreases the effect of the psychological refractory period.