In this study, a modified silica gel surface with a hydrophobic ionic liquid (SG-1,10-PhenanNTf₂) was used as an adsorbent for a selective extraction of coumarin prior to its determination by use of high performance liquid chromatography. Results demonstrated that SG-1,10-PhenanNTf₂ phase had a good adsorption capacity up to 85.29 mg?g^?1, high selectivity, good site accessibility and fast binding kinetics toward coumarin. The adsorption capacity for coumarin was improved by 62.33% with the SG-1,10-PhenanNTf₂ phase as compared to activated silica gel. Adsorption isotherm data displayed that the adsorption process was mainly monolayer on a homogeneous adsorbent surface, confirming the validity of Langmuir adsorption isotherm model. The adsorption of coumarin on the SG-1,10-PhenanNTf₂ phase was accomplished after only 60 min contact time. Results of kinetic models showed that the adsorption of coumarin on the SG-1,10-PhenanNTf₂ phase obeyed a pseudo second-order kinetic model. Finally, the efficiency of this methodology was confirmed by applying it to real water samples.