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Surface nitrogen complexes formation upon reaction of coal char with NO at 270 °C in the presence or absence of O₂ and/or H₂O was studied by XPS. Complexes such as pyrrolic-N type, pyridine-N-oxide, pyridinic-N and –NO₂ were observed. The major increment was in pyridinic-N. Water had a partial inhibition effect while oxygen promotes the formation of the nitrogen complexes probably due to char gasification. The gasification level in mixtures with O₂ varied according to the presence or not of H₂O. TPD was used to quantify reversible NO adsorption and oxygen surface groups formed on the char during reaction. Molecular modeling was applied to determine the thermodynamics of the reactions. Mechanisms are proposed to explain the formation of pyridinic and –NO₂ complexes at low temperatures.