A rare example of a reversible recognition of Nd3+ by a newly synthesized molecular receptor (L-1), having a diazo group as the reporter functionality, is reported. Studies revealed that this receptor eventually forms a [Nd3+](2)L-1 type complex, through the formation of the intermediate complex [Nd3+]center dot L-1 following a two-step equilibrium process. Respective equilibrium constants for two successive processes were evaluated based on data obtained from the systematic fluorescence titration. Formation of [Nd3+](2)L-1 caused a detectable change in color, and associated affinity constants were also evaluated from spectrophotometric titration data. A rather unusual binding mode of L-1 for Nd3+ ion is established by various spectroscopic studies. The remarkable specificity of L-1 for Nd3+, constitutes a rare example of a highly selective receptor for this ion in the presence of excess of all other lanthanide ions.