The objective of this research was to design and characterize montelukast sodium (MS) loaded novel nanosized and biocompatible Kollidon (R) SR nanoparticles to provide prolonged release behavior that can improve bioavailability, reduce side effects and give better efficacy in the therapy of chronic asthma. Particle size and zeta potential measurements, morphological, thermal, FTIR, NMR analyses, MS quantification by modified HPLC method were used for characterizing the formulations prepared. Cytotoxicity studies were realized to confirm the safety of formulations. Formulations showed smaller particle size (421-438 nm) with narrow size distribution and negatively charged characteristics. Drug release was extended more than 10 fold with nanoparticles indicated diffusion controlled release from polymeric matrix. Cytotoxicy studies revealed the safety and biocompatibility of the particles with higher cell viability values than MS. These findings suggest that MS loaded nanoparticles seem to be a promising drug delivery system for the sustained release of MS.