Many researchers have investigated the usage of carbonaceous materials as adsorbents. In this study, boron carbon nitride (BCN) was synthesized using boric acid and melamine as precursors and its performance in the adsorptive removal of methylene blue (MB) dye from aqueous solutions was investigated. The structure of the synthesized BCN was identified using a scanning electron microscope (SEM), X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and Fourier transform infrared-attenuated total reflection (FTIR-ATR) analyses. From the SEM analysis, the graphite-like layered structure of BCN was observed. Additionally, the stoichiometry of BCN was obtained as B2.2CN2.9O6.1. The adsorption studies were performed under different conditions to obtain the parameters such as contact time (0-150 min), adsorbent dosage (0.01-0.20 g), initial concentration (10-50 mg/L), and initial pH (2-12). The isotherm applicability order was identified as Langmuir > Freundlich > Flory - Huggins > D - R > Harkins - Jura. According to this order, the Langmuir isotherm was determined to be the most feasible isotherm for the adsorption process, based on the assumption that adsorption occurs in a single layer on adsorbent surfaces with homogeneous pore distribution. Besides, the q(m) value was determined from the Langmuir model as 212.8 mg/g at 25 degrees C. It was found that the adsorption followed the pseudo-second-order based on kinetic studies. In addition, it was determined that the adsorption from thermodynamic parameters occurred endothermically (Delta H degrees = 10.2kJ/mol) and spontaneously (Delta G(298)(o) = -28.7kJ/mol). All of these results suggest that BCN could be employed as an adsorbent for the removal of dyes from an aqueous medium.