Quorum quenching using different kinds of inhibitors is a new subject of research that is used for biofilm prevention in wastewater treatment membrane systems. In this study, three natural compounds, namely tea, coffee and vanillin, were tested in order to evaluate their possible effects on wastewater sludge characteristics in a batch type aerobic reactor. The parameters evaluated included the soluble microbial products (total soluble microbial products, protein and carbohydrate fraction of soluble microbial products), extracellular polymeric substance concentrations (total extrapolymeric substances, protein and carbohydrate fraction of the extrapolymeric substances), floc size, zeta potential, sludge volume index and capillary suction time. The effects of these plant based compounds upon the quorum sensing N-butyryl-L-homoserine lactone signal were also investigated using gas chromatography - mass spectrometry (GC-MS) under optimized conditions. The results indicated different effects for each natural compound upon the sludge characteristics. The role of these natural compounds as quorum quenchers in the batch-type aerobic reactor was inconclusive due to their effects on extraction outputs. Understanding the effect of quorum quenchers on sludge characteristics is important and recent studies have been aimed at preventing biofilm formation in membrane bioreactors.