In this study, first, magnetic nanoparticles (MNP) were synthesized using a coprecipitation method and the synthesized particles were characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic light scattering (DLS), and vibrating sample magnetometry (VSM). According to DLS and VSM analyses results, it was seen that the size of the MNP was smaller than 10 nm and they exhibited superparamagnetic properties, respectively. Then, magnetic Fe3O4-chitosan micro/nanoparticles were synthesized using a suspension cross-linking method in the presence of the MNP. Fe3O4-chitosan microparticles (Fe3O4-CMs) and Fe3O4-chitosan nanoparticles (Fe3O4-CNs), which have different structural, morphological, and magnetic properties, were obtained. All of the particles were characterized using transmission electron microscopy (TEM), FTIR, TGA, DLS, and VSM. In the second part of the study, the dye adsorption properties of the two different adsorbents from aqueous solution were investigated. For these purposes, Bromothymol Blue (BB) was used as a dye and the parameters affecting adsorption of BB (contact time, initial dye concentration, temperature and pH) were investigated. When the optimum adsorption conditions were provided for each adsorbent, the adsorption capacities of Fe3O4-CNs and Fe3O4-CMs were 82.2 and 193.3 mg/g, respectively.