In this work, we initially describe the preparation of magnetic and fluorescent nanocomposites (MF NCs) based on polystyrene/tetraphenylporphyrin/maghemite (PS/TPP/gamma-Fe2O3). After carrying a series of exploratory experiments, we have found that the composite that presented the highest values of fluorescence intensity and magnetization (Si samples) was obtained when we employed 1 mL of TPP and 1% of PS. When tested as photosensitizer agents for the inactivation of the pathogenic bacteria Escherichia coli, these MF NCs presented excellent antibacterial activity, indicating that they can be promising candidates to inactivate microorganisms dispersed in aqueous solutions. Taking into account this peculiar combination of outstanding properties and simple and low cost synthesis, we suggest that this kind of NC could find widespread use in environmental and biomedical applications. (C) 2015 Elsevier B.V. All rights reserved.