Mixed species biofilms exhibit increased tolerance to a number of stresses compared to single species biofilms. The aim of this study was to examine the effect of grazing by the heterotrophic protist, Tetrahymena pyriformis, on a mixed species biofilm consisting of Pseudomonas aeruginosa, Pseudomonas protegens and Klebsiella pneumoniae. The spatial organization and quantification of fluorescently tagged strains within the biofilm was determined by confocal microscopy. Protozoan grazing significantly reduced the single species K. pneumoniae biofilm, and while the single species P. protegens biofilm also displayed sensitivity to grazing, the biofilm biovolume was not significantly affected. Unlike K. pneumoniae and P. protegens biofilms, P. aeruginosa biofilms exhibited grazing resistance to predation by T. pyriformis. Additionally, mixed species biofilms containing P. aeruginosa also displayed grazing resistance, indicating that the sensitive strains gained associational resistance to predation by T. pyriformis. Rhamnolipids produced by P. aeruginosa were shown to be toxic for the protist. However, a rhamnolipid-defective mutant strain of P. aeruginosa maintained grazing resistance, which suggests that predation protection is a multifactorial phenotype. A single species biofilm of a mutant of P. aeruginosa lacking rhamnolipids and the type III secretion system was grazing resistant. However, the overall grazing tolerance of the biofilm was reduced when the single and double knockout mutants of P. aeruginosa were introduced to the mixed species biofilm, suggesting that both play partial roles in predation resistance. This study demonstrates that residing in a mixed species biofilm can be an advantageous strategy for grazing sensitive bacterial species, as P. aeruginosa protects the whole community from protozoan grazing.