The insufficient bond strength of carbon fibers (CFs) towards cementitious matrices limits at present their prospective application as CF-reinforcement in construction. In this investigation an oxygen plasma modification process was utilized to tailor the surface properties of CF rovings in achieving higher affinity towards mineral-based aqueous suspensions. A systematic study on various process parameters was performed to outline expedient treatment regimes. X-ray photoelectron spectroscopy, single fiber tensile tests, and Weibull-analysis delivered insights on the effects of plasma modification on the carbon fibers’ properties. Mineral-impregnated carbon fiber (MCF) reinforcement bars were produced and characterized by means of pullout tests. It was found that short plasma treatment time, high oxygen flow rates, low pressure, and long pulse duration improved the shear strengths of the MCF bonds on being extracted from the concrete matrix. Morphological analysis revealed that a higher oxygen concentration enables better wetting behavior towards the mineral matrices and, hence, yields higher bond strength.