Magnetic iron oxide nanoparticles (MIONPs) were newly synthesised and then modified by cetyltrimethylammonium bromide (CTAB) for solid phase extraction, preconcentration and determination of valsartan (VAL) followed by high performance liquid chromatographic analysis. The synthesised magnetic Fe3O4 nanoparticles were used as adsorbent and methanol was used as desorbing solvent. The separation was performed using a RP-C18 BDS hypersil chromatographic column and an isocratic mobile phase consisting of phosphate buffer (0.03 M):acetonitrile:methanol (40:40:20%). A diode array detector at wave length 210 nm was used. Chromatographic analysis time was less than 5 minutes per sample with complete resolution of VAL from the different studied matrices components (tR of VAL = 4.20 minutes). Important parameters such as adsorbent and CTAB volume, extraction time and desorption solvent type and time were optimised. A good linear response was obtained in the concentration range of 10–150 ng/mL with determination coefficient (r2) of 0.9998. Limits of detection and quantification were found to be 2.02 and 6.72 ng/mL. The proposed method was applied successfully for determination of VAL in raw material,aqueous environmental samples, biological samples, tablet dosage forms with good recovery values indicating high accuracy of the method.