Bioactive dressing based on bacterial cellulose modified with carboxymethyl groups (mBC) was successfully prepared and studied. The surface of mBC was activated using carbodiimide chemistry and decorated with alginate/hydroxypropyl cellulose submicroparticles containing dexamethasone phosphate (DEX-P). Prior to their deposition particles were coated with chitosan in order to facilitate their binding to mBC, and to increase the control over the release process. The detailed physicochemical characterization of the particles and the bioactive dressing was performed, including the determination of the particles' size and size distribution, DEX-P encapsulation efficiency and loading, particles' distribution on the surface of the mBC membrane, as well as DEX-P release profiles from free and mBC-bound particles. Finally, the preliminary cytotoxicity studies were performed. The fabricated bioactive material releases DEX-P in a controlled manner for as long as 25 h. Biological tests in vitro indicated that the dexamethasone-containing submicroparticles are not toxic toward fibroblasts, while effectively inhibiting their proliferation. The prepared bioactive dressing may be applied in the treatment of the post-operative wounds in the therapy of keloids and in other fibrosis-related therapies.