Background: The exact prevalence and distinct clinical and histological criteria of psoriatic lesions in the oral cavity remain unknown. Although some non-specific lesions are more frequent in psoriatic patients in comparison with healthy people, the incidence and clinical variation of psoriasis are heterogeneous in the literature. Objectives: This study aimed to evaluate the incidence of oral lesions in Iranian patients with psoriasis. Methods: Patients with plaque-type psoriasis were participated in a cross-sectional study. Physicians performed full-body skin examination and assessed extra-cutaneous involvement including oral cavity, nails and articular system. Results: One hundred patients with psoriasis (41 males and 59 females) with the mean age of 43.79 ± 12.52 years were participated in the study. Mucosal changes clinically suggestive of oral psoriasis were detected in none of the cases. We observed nonspecific oral lesions in 48% of the patients including fissured tongue (35%), angular cheilitis (13%), actinic cheilitis (11%), geographic tongue (6%), fibroma (3%) and denture stomatitis (2%). The statistical analyses showed that presentation of oral lesions increases with concomitant cardiovascular disorders or diabetes mellitus, but no relationship between oral lesions and other demographic and clinical data was noted. Conclusions: Although the incidence of true oral psoriasis is rare, non-specific oral lesions may be frequently found in patients with psoriasis. Since both true psoriatic oral lesions and non-specific changes are mostly asymptomatic, routine examination of the oral cavity is necessary in all patients with the diagnosis of psoriasis.