Magnetic cellulose nanoparticles (MCNPs) coated with 1-butyl-3-methylimidazolium hexafluoro phosphate [C4MIM][PF6] ionic liquid (IL) through electrostatic interactions are proposed for the first time as sorbents in a magnetic solid phase extraction (MSPE) method for the determination of paracetamol (PAR), ibuprofen (IBU), naproxen (NAP) and diclofenac (DIC) in natural waters. The parameters that affect adsorption (dispersive solvent, amount of IL, pH and salt content) and desorption (desorption solvent, type of energy and time) were studied. The values that provided the maximum adsorption efficiency and extraction recovery were selected as optimum conditions for adsorption and desorption, respectively. Under the optimum conditions, the adsorption and desorption of all analytes was simultaneous and quantitative. High performance liquid chromatography (HPLC) with ultra violet (UV) and fluorescence (FL) detector was used after the sample preparation. The precision, expressed as relative standard deviation was between 1.4 and 7.6%. Limits of detection and quantification were in the range 3.2–7.2 μg L− 1 and 11–24 μg L− 1, respectively. Moreover, the proposed method provides enrichment factors from 29.0 to 34.2. Recovery studies on 10 mL of spiked tap, river and dam water samples at 50 and 100 μg L− 1 were carried out. The extraction recoveries were from 85 to 116%, and were in a comparable range regardless of the type of water. The method is simple, rapid, and environmentally friendly. © 2017 Elsevier B.V.