In this study, hexagonal boron nitride (BN) with a sheet-like morphology is successfully synthesized by reacting borax (Na2B4O7·10H2O) and urea (CO(NH2)2) powders in air via a facile microwave-assisted method within a short reaction time (15 min). The as-prepared product is structurally characterized via Fourier transformation infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersion X-ray analyzer (EDX), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) surface area measurements. The adsorption process of methyl violet (MV) as a model of organic dyes and ciprofloxacin (CIP) as a model of antibiotics onto the boron nitride nanosheets has been experimentally and theoretically studied. The BN nanosheets exhibit the maximum adsorption capacity of 320.94 mg g-1 for MV dye and 266.29 mg g-1 for CIP antibiotic. The Freundlich isotherm model was suitable to describe the adsorption equilibrium isotherm data and the pseudo second-order model reflected the adsorption kinetics well. The calculated thermodynamic parameters show that the adsorption process is spontaneous under the measured conditions. The adsorption of CIP, MV and CIP + MV molecules on the surface of BN has been investigated through DFT calculations. The charge transfer and high adsorption capacity demonstrate the potential of BN nanosheets as an adsorbent for the simultaneous removal of MV dye and CIP drug from contaminated water.