OBJECTIVE : We aimed to determine if there was any association between geographic tongue (GT) and fissured tongue with ABO blood group among adult psoriasis patients in Saudi Arabia. METHODS : This hospital-based cross-sectional study included 100 consecutive new adult patients diagnosed with psoriasis and 100 case-matched participants in the control group (nonpsoriatic). Sociodemographic and dermatologic parameters, intraoral lesions (GT and fissured tongue), and ABO blood grouping and immunoglobulins were recorded and evaluated using χ2 or Fisher's exact test. RESULTS : A total of 74% of patients had an early age of onset, and 48% of them reported this disease in their parents. A total of 76% of those with generalized psoriasis had plaque type, whereas 78% with the localized type had pustular lesions. A total of 70% of psoriatic patients had O Rh-positive blood; 63% of tongue lesions seen in these patients were GT, and it was most prominent in O Rh-positive (64.28%) and O Rh-negative (62.50%) blood types. GT was prevalent among women (75.6%). CONCLUSIONS : This study found a positive association of both GT and fissured tongue in this population of adult patients with psoriasis compared with a case-matched control population without psoriasis.