Palladium based catalysts particularly nanoscale palladium particles have recently drawn enormous attention due to their versatile role in organic synthesis. In this thesis, palladium nanoparticles supported on styrene-divinylbenzene were synthesized and used as heterogeneous catalyst in organic synthesis. For this reason, at first tris(dibenzyliden- eacetone)dipalladium(0) complex was prepared by treating the system PdCl 2 /dba/NaOAc to give a dark purple precipitate. The precipitate was removed, washed and recrystallized. Pd- was synthesized using an in-situ technique in which prepared Pd 2 (dba) 3 /butan-1-ol/styrene/divinylbenzene was used as the precursors of the catalyst. The mixture was stirred at 90 °C for 6h and after cooling to r.t, AIBN initiator was added and the mixture was further stirred at 90 °C for 4h. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the palladium particles were well-dispersed within the polymer matrix and were typically about 50 nm in diameter. The catalyst was crushed into a gray powder and used for Suzuki coupling and oxidation reaction of alcohols and showed excellent yields. The recyclability of catalyst was tested and results indicated that S-dvb stabilized pd(0) nanoparticles catalysts could be reused in several successive runs without significant loss of initial activity. In the present study, we have also investigated application of the palladacycle [Pd (µ-C1) (hy;(OPh) 2 (OC 6 H 4 )] 2 as an efficient catalyst for the Suzuki and Heck cross-coupling reactions of various aryl halides. In the Suzuki reactions, the corresponding products were obtained with yields in the range 40–100% and 25–100% in the Heck reactions. It is the advantage of these methods that Suzuki reaction of aryl halides with arylboronic acid was done at room temperature and the Heck reaction was worked well also in air, thus simplifying the work-up of the catalytic process.