A species of powdery mildew on Pistacia chinensis Bunge (Anacardiaceae) with both longer and shorter types of appendages on the same perithecium was collected from Nanjing, Jiangsu Prov. and identified as Uncinuliella pistaciae sp. nov. owing to its distinctive morphology and host specialization. Anacardiaceae is a new record of host family for Uncinuliella.