Activated carbon (AC) was modified by the coprecipitation method to induce magnetic properties for the removal of isonicotinic acid (iNA). Magnetization was done by using salts of Fe2+ and Fe3+ as precursors. The induced magnetism in magnetic activated carbon (MAC) was confirmed by Fourier transform infrared and field-emission scanning electron microscopy-electron diffraction spectroscopy analyses. Also, the stability of both AC and MAC was tested by TGA. Batch adsorption experiments were performed using both AC and MAC to see the effects of adsorption time (0-180 min), adsorbent amount (12-40 g/L for AC and 4-80 g/L for MAC), initial iNA concentration (1.23-6.16 g/L), and temperature (298-333 K) on the removal efficiency. Steady state was reached at 120 min by using both adsorbents. Equilibrium data was best fitted by Langmuir and Temkin isotherms for AC and MAC, respectively. The maximum adsorption capacities were noted to be 0.406 g/g of AC and 0.071 g/g of MAC. Pseudo-second-order model fitted the kinetic data for both adsorbents. The magnetic property in MAC ensured easy separation of adsorbent using magnet after adsorption from the aqueous medium.