Tinea incognito is the result of lack of diagnosis of dermatophyte infection of the glabrous skin and the misuse of steroids or calcineurin inhibitors. In this case report a 20-years-old female patient diagnosed as tinea incognito and Trichophyton rubrum isolated from her skin lesions, was presented. The patient suffered from an itchy skin lesion on her neck and right breast. Physical examination revealed and plaques with erythema and papules on neck and breast area. The patient had used several corticosteroids suggested by dermatologists for 10 months. Direct microscopic examination of the skin scrapings with 10% potassium hydroxide preparation revealed fungal elements and Trichophyton rubrum was isolated in culture. Use of corticosteroids was ceased and terbinafine (250 mg tb and cream) therapy was initiated to continue for four weeks. Following treatment, total clinical and mycological cure was established. It was concluded that tinea incognito which was not a rare clinical entity, could be presented in various clinical forms and usually resulted from the wrong treatmeril: modalities. Thus atypical erythematous plaques should be investigated in terms of presence of fungi and treated accordingly to establish total clinical and mycological cure.