Hypothesis: Effective removal of oil pollutants from the surface of water is important in oil-polluted environments. Since living microorganisms can be used as particle-stabilizers for oil emulsification, magnet-responsive oil-degrading bacteria (M-Bacteria) are expected to integrate three intriguing properties, such as Pickering emulsification, magnet-responsiveness and bioactivity. Hence, by acting as an efficient Pickering emulsifier to encapsulate oil pollutants, it should be possible to eliminate oil from water under the application of an external magnetic field. Experiments: Oil-degrading bacteria, Brevibacillus parabrev, were successfully coated with a shell of magnetic Fe3O4 nanoparticles using polycations. The morphology and physicochemical characteristics of M-Bacteria were characterized by various techniques. A systematic study on Pickering emulsification of M-Bacteria and the removal of five types of oils were performed. Specific adsorption of M-Bacteria at the oil droplet surface was observed through optical, fluorescence, and scanning electronic microscopy images. The biodegradation process of oil was monitored using gas chromatography. Findings: Eco-friendly M-Bacteria not only acts as an effective particle emulsifier to realize encapsulation and magnetic separation of oil contaminants but also shows a strong ability for further conversion of oil. This is the first report of oil removal via Pickering emulsification of living bacterial cells, which shows the potential of bacterial cells as functional colloidal materials in treating oily wastewater. (C) 2019 Elsevier Inc. All rights reserved.