The adsorption kinetics of thermodynamically immiscible polymer mixtures on nonporous adsorbent, viz., fumed silica and fumed silica modified by diethylene glycol from a common solvent (CCl4), have been studied for a wide concentration range, including the crossover from dilute to semidilute regions (C < C*, C = C*, C > C*). Polystyrene (PS) and polybutyl methacrylate (PBMA) with different crossover concentrations have been studied. The structure of the adsorption layer has been characterized by the value of the fraction of bound segment (P) that provides insight into the conformation of adsorbed macromolecules. Comparison of these results with adsorption isotherms shows a reverse correlation between adsorption value and P, both for solutions of pure polymers and for their mixtures, for the case of a molecular aggregative mechanism of adsorption, It has been shown that the establishment of adsorption equilibrium in solutions of polymer mixtures occurs in two stages, namely, a fast stage and a slow stage. The character of kinetic dependencies is determined by the concentrations of components and the nature of the adsorbent. The main factors influencing the adsorption kinetics are the solution mode (diluted or semidiluted) and the thermodynamic compatibility of polymers in solution. For solutions of PS and PBMA mixtures at concentrations above C* the establishment of adsorption equilibrium is more prolonged. The existence of an entanglement network slows the adsorption processes.