Abstract: In this study, petrography, mineral chemistry, geochemistry ,and petrology of Oligocene-Miocene volcanicrocks located in the Büyükbostancı-Çiçekpınar (Balıkesir, NW Turkey) region in the south of Balıkesir wereinvestigated.The studied volcanics rocks have the composition of andesite, basaltic andesite, trachyandesite ,andaccompanying pyroclastics. Volcanic rocks show microlithic porphyry, porphyric, fluidal, glomeroporphyritic andspherulitic structures ,and consist of plagioclase, clinopyroxene, amphibole, biotite ,and Fe-Ti oxide as the majorminerals. According to the results of mineral chemistry analysis of the investigated volcanic rocks, plagioclasesare andesine (An33-47Ab49-61Or2-6) ,and labradorite (An60-62Ab34-38Or1-4), pyroxenes are augite ,and clinoenstatite(Wo43En75Fs36-Wo1En38Fs14) ,and biotite is Mg-bearing biotite. Geothermobarometry calculations from biotite yieldeda temperature range of 798–843 °C ,and a pressure range of 0.67–1.93 kbar. Geochemically, the volcanic rocks have high-K calc-alkaline features. Fractional crystallization ,and assimilationprocesses dominated by hornblende, clinopyroxene ,and biotite mineral differentiation affected the andesitic volcanicrocks. Trace element diagram for volcanic rocks normalized to normal-mid-ocean ridge basalts (N-MORB) showenrichment in large ion lithophile elements (LILE, Rb, U ,and Th) ,and depletion in high field strength elements(HFSE, Nb ,and Yb). In the rare earth element diagram normalized to chondrite, there is moderate enrichment of (La/Lu)N 8.29-15.65 ,and the curve generally has a concave shape. When the obtained data ,and regional geological dataare evaluated together, the investigated volcanic rocks are post-collisional products with subduction traces ,and arederived from enriched lithospheric mantle.