Abstract Spills due to the floating oil on the surface of sea water shows a significant alteration in the natural phenomenon of the marine ecosystem. Hence, amphiphilic sodium salt of oleoyl carboxymethyl chitosan (NaO-CMCS) was synthesized, characterized and studied as a sustainable adsorbent for the removal of floating oil in the oil spill treatment. Successful chemical modification of chitosan was confirmed by chemical analysis using Fourier Transform Infrared (FTIR), ¹H Nuclear Magnetic Resonance (¹H NMR), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS) and Elemental Analyzer. The effect of pH and salinity on the surface charge of NaO-CMCS was studied. Marine diesel was chosen as an oil phase for the emulsion studies. Hydrophobically modified NaO-CMCS shows the oil-in-water (o/w) emulsion stability for more than 6 weeks with droplet size ≤ 30 μm which increases with decreasing temperature. The behavior of emulsion with different salinity shows phase separation at pH 5, bridging flocculation at pH 6–7 and o/w emulsion at pH 8. Calcium ions act as a cross-linker between two carboxylic acid groups of NaO-CMCS, enhancing the removal of oil from the creamy emulsion. The recovery of oil was 75–85% and 19–49% from deionized water and sea water, respectively. Oil was not chemically altered during the recovery, demonstrating the effectiveness of this derivative in the oil spill response for the removal and recovery of floating oil from the sea water.