Monospecies and mixed bacterial biofilms of Rhodococcus ruber gt1, Pseudomonas fluorescens C2, Alcaligenes faecalis 2, and Rh. erythropolis 11-2 were obtained during growth in presence of the carriers. The transformation of aliphatic and aromatic nitriles by the biofilms of nitrile-hydrolyzing bacteria, as well as the growth dynamics of Rh. ruber gt1 and P. fluorescens C2 biofilms and their resistance to toxic substrates and products of nitrile hydrolysis, were studied. It was shown that the P. fluorescens C2 biofilm mass and total ATP content reached the maxima after 1 day of growth, whereas Rh. ruber gt1 reached them after 3–4 days of cultivation. The biofilms of Rh. ruber gt1 and P. fluorescens C2 were more resistant to the effects of high concentrations of acrylamide and acrylonitrile and had a greater adaptive capacity than planktonic cells.