A 30-year-old woman presented to a dermatology outpatient department with a 6-month history of pruritic, violaceous-to-hyperpigmented lesions on the trunk. The lesions were predominantly confluent in areas exposed to friction from undergarments and had gradually progressed, with occasional excoriation and oozing. Clinical examination revealed reticulated violaceous plaques on the chest and back, accompanied by isolated papules on the right side of the abdomen. Dermoscopy demonstrated Wickham striae, suggesting a lichenoid disorder. Allergic contact dermatitis was initially considered because of the distribution of the lesions; however, patch testing yielded negative results. Histopathological examination showed hyperkeratosis, hypergranulosis, vacuolar degeneration of the basal layer, a band-like lymphocytic infiltrate, and pigment incontinence, supporting the diagnosis of confluent lichen planus. The distribution of the lesions suggested that chronic friction may have contributed to their development through the Koebner phenomenon. Treatment with topical clobetasol propionate and oral antihistamines resulted in significant improvement within 2 months. No recurrence was observed during 6 months of follow-up. This case illustrates the diagnostic challenge posed by confluent lichen planus mimicking contact dermatitis and highlights the complementary roles of dermoscopy, patch testing, and histopathological examination in establishing the diagnosis.