Petrographic and geochemical data are provided for the Koli-Gomer area granitoids, which is a part of the Blue Nile Gorge in western Ethiopia. The petrography and geochemistry of the KoliGomer area granitoid rocks have not been studied. The present research work aims to analyze and interpret the geological, petrographic, and geochemical characteristics of granitoid rocks by using the whole rock geochemical analysis method integrated with petrographic and field observation. Field observation shows that the studied area is dominated by plutonic rocks with some metamorphic rocks, and the area is affected by different geological structures like veins, joints, faults, dykes, and foliation. Petrographically, the studied granitoids are mainly composed of alkali-feldspar minerals, quartz, plagioclase, biotite, hornblende, pyroxene, opaque minerals, and other accessory minerals. From geochemical data, the negative correlation of SiO versus other major oxides like Al 2 O 3 , MgO, CaO, FeOt, TiO 2 , P 2 O and trace elements like V, Ti, Sc, and Cr shows decreasing trends that indicate the characteristics of mineral fractionation trends in the early crystalizing phase that controls the evolution of magma. Their tectonic setting is volcanic arc granitoid, which resembles a subduction zone arc environment. The negative Eu anomaly and depletion in Sr, P, and Ti anomalies imply the fractionation of plagioclase, apatite, and titanite crystals, respectively. The variation in compatible and incompatible trace elements integrated with different binary plots suggests that most of the studied area's granitic rocks are Itype and some S-type granites, which were formed through partial melting of crustal involvement and/or by fractional crystallization from source magma that originated in the mantle. Further findings show that the granitoids in the study area consist of gabbroic to granitic units, some ferroan to magnesian, sub-alkalic magma series, and metaluminous to peraluminous magma sources. The Koli-Gomer granitoids are the one features of the East African orogeny. 5, 2