The objective of this study was to prepare composite materials based on mesoporous silica/carbon, functionalized with acid groups, and also to analyze its application in the adsorption of dyes. These materials were prepared in a simplified unconventional route. The carbon phase was generated by direct carbonization of organic surface-active templates, which are used in the synthesis of meso-ordered silicas. The resulting composite materials were characterized in terms of their structure, texture, chemical composition, and surface chemical reactivity. Data obtained demonstrate uniform and ordered porous structures of approximately 70–200 Å, with a developed surface area of approximately 400–500 m2 g−1 and a large total pore volume of approximately 1.0–1.5 cm3 g−1. The potential of synthesized composite materials functionalized by oxygenated groups as adsorbents of cationic dyes was analyzed, the values of the maximum adsorption capacity between 317 mg g−1 and 245 mg g−1 were obtained. The adsorbing properties of silica/carbon composite materials obtained in an unconventional method using an organic template as the only carbon source were compared with the properties of silica/carbon composite materials manufactured by the conventional method using external precursors of the carbon phase. It has been proved that composite materials synthesized using an unconventional procedure, despite the fact that they have a lower carbon phase content, exhibit adsorption properties that are comparable or superior to materials elaborated in the traditional way, removing up to 85–90% of methylene blue from water contaminated with dye.