Introduction: Generalized Anxiety Disorder (GAD) is characterized by chronic worry and impairments in cognitive functions, particularly attention, and is associated with alterations in brain wave patterns. Neurophysiological evidence highlights the critical role of alpha and theta oscillations in emotion regulation and attentional processes. The present study aimed to investigate the effectiveness of transcranial direct current stimulation (tDCS) in modulating the absolute power of brain waves and improving visual and auditory attention in individuals with GAD. Methods: This randomized, single-blind clinical trial was conducted on 24 individuals aged 18–40 years diagnosed with GAD in Tabriz. Following psychiatric evaluation and screening using the Spitzer Generalized Anxiety Disorder Questionnaire, participants were randomly assigned to experimental and control groups (n = 12 each). Visual and auditory attentional performance and absolute power of brain waves were assessed using an integrated attention test and quantitative electroencephalography (qEEG) before and after the intervention. The experimental group received 17 sessions of tDCS (2 mA, 24 minutes) targeting the orbitofrontal cortex, while the control group received sham stimulation. Data were analyzed using SPSS version 20. Results: Statistical analyses revealed a significant association between changes in brain wave activity and levels of visual and auditory attention in individuals with GAD. Specifically, absolute power of theta and delta bands showed a significant decrease, whereas alpha and beta power demonstrated a significant increase. Moreover, mean visual attention scores increased from 596.86 to 1836.34, and auditory attention scores rose from 503.57 to 1850.30, indicating substantial improvement following the intervention. Conclusion: The findings suggest that transcranial direct current stimulation effectively modulates electrophysiological brain activity and leads to significant improvements in visual and auditory attention in individuals with generalized anxiety disorder. These results support the use of tDCS as a complementary, non-invasive intervention in the treatment of anxiety disorders.