In recent years, graphene oxide has been considered as a soluble precursor of graphene for electronic applications. However, the performance lags behind that of graphene due to lattice defects. Here, the relation between the density of defects in the range of 0.2 % and 1.5 % and the transport properties is quantitatively studied. Therefore, the related flakes of monolayers of graphene were prepared from oxo‐functionalized graphene (oxo‐G). The morphologic structure of oxo‐G was imaged by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). Field‐effect mobility values were determined to range between 0.3 cm2 V−1 s−1 and 33.2 cm2 V−1 s−1, which were inversely proportional to the density of defects. These results provide the first quantitative description of the density of defects and transport properties, which plays an important role for potential applications.