This is a prospective, double-blind, randomized controlled trial evaluating the efficacy and safety of active transcranial direct current stimulation (tDCS) as an adjunctive treatment compared to sham tDCS in adults aged 18 to 60 years with treatment-resistant obsessive-compulsive disorder (OCD). Participants must have a Yale-Brown Obsessive Compulsive Scale (Y-BOCS) score more than or equal to 16 and be on stable standard care (SSRIs at therapeutic doses for more than or equal to 12 weeks, with or without CBT). The study aims to recruit 124 participants (62 per group) from the Department of Psychiatry at a tertiary care hospital in Western Maharashtra, India. Intervention involves 10 daily sessions over 2 weeks: active tDCS delivers 2 mA for 20 minutes with anodal placement over the left deltoid (extracephalic) and cathodal over the supplementary motor area (SMA); sham tDCS mimics the setup without active current. Primary outcome is the change in Y-BOCS scores from baseline to 6 weeks post-intervention, with secondary outcomes including adverse effects and tolerability. Follow-up assessments occur at 2 and 6 weeks. The trial duration is 18 months, with statistical analysis using paired t-tests for within-group changes and independent t-tests/Mann-Whitney U for between-group comparisons (p less than 0.05 significant). This study addresses gaps in non-invasive neuromodulation for OCD, building on prior evidence of tDCS’s potential to enhance cortical excitability and reduce symptoms.