In this study, it is aimed to determine the mineralogical characteristics of Middle-Upper Miocene clayey rocks of Van formation and to interpret the paleoclimate conditions during Middle and Late Miocene in which the rocks were formed. The study area is located in the Southeast of Lake Van. Four stratigraphic sections were measured from the Middle-Upper Miocene rocks and 73 clayey rock samples were collected along these sections. All samples were analysed by X-ray diffraction to identify mineralogical compositions. Quartz, feldspar, mica, calcite, dolomite, amphibole cristobalite and clay minerals were determined in bulk compositions of the samples. Clay fractions include smectite, illite, chlorite, serpentine, chlorite-smectite and illite-smectite mixed layers. SEM and EDX studies were performed on three selected samples. In these samples, clay minerals such as serpentine, chlorite and smectite were observed. Based on the coexistence of well-crystalline illite, chlorite, smectite and feldspar minerals, it has been interpreted that cold, dry climate conditions prevailed in the region during the formation of the Van formation clastic rocks.