This study explains some electronic and structural parameters of niacin (NA) encapsulation into PAMAM-G1 dendrimer using DFT calculations. Optimized structural geometries, interaction energies, NMR, NBO, and AIM analyses, in accordance with experiment, revealed that the stability of G1@NA complex can be attributed to the five intermolecular hydrogen bonds formed between the functional groups of G1 and NA. Because of nearing to the experimental results, all the calculations repeated again using a self consistent reaction field (SCRF) and the polarizable continuum model (PCM) to address the implicit solvent effects and the obtained results were in line with the calculations in gas phase. (C) 2017 Published by Elsevier B.V.