In the present work, poly(1,8-diaminonaphthalene) (poly(1,8-DAN)) was synthesized by chemical oxidation of 1,8-diaminonaphthalene (1,8-DAN) monomer with ammonium persulfate (APS) oxidant and it was used in the adsorption of selenite ions. The polymer samples synthesized at various molar ratios of 1,8-DAN to APS were characterized by FTIR analysis and they were used in the adsorption experiments. The effects of initial acidity, the molar ratio, and initial selenium concentration on the adsorption behavior of poly(1,8-DAN) were examined by using batch adsorption technique. It was found that selenite was adsorbed onto poly(1,8-DAN) in strong acidic conditions (3-8 M HCl). The experimental adsorption data were applied to the Langmuir and Freundlich isotherms. The adsorption capacities of the polymer samples at the molar ratios of 1/0.5 and 1/2 were calculated as 75.19 and 45.05 mg Se/g, respectively. It was estimated that the adsorption mechanisms of selenite ions onto poly(1,8-DAN) were governed by electrostatic interaction (>NH2+SeOCl3-) and piazoselenol type binding (-N=Se=N-).