The aim of this study is to determine the physical and rheological properties of cross-linked lineer low density polyethylene (LLDPE) with different concentration of peroxide. Tert-butyl cumyl peroxide (BCUP) was used in crosslinking. The peroxide concentration was changed as 0.5, 1, 2 and 3 phr. LLDPE/Peroxide blends were prepared by melt compounding process using an Xplore Instruments laboratory compounder at 135 deg.C barrel temperature. The crosslinking was carried out using a hot-press operated at 175 deg.C. At the characterization stage; tensile test for mechanical properties, differential scanning calorimetry (DSC) for thermal characterization, rheometer analysis for rheological properties and Fourier transform infrared spectroscopy (FTIR) for structural properties were investigated. It was found that the addition of peroxide to LLDPE increased degree of cross-linking for rheological tests. According to tensile tests, elongation at break of blends increased with increasing peroxide content. The plastic flow behavior during tensile testing for uncrosslinked LLDPE changed into an elastomeric behaviour with increasing strength upon elongation. It was observed that the peroxide concentration was also effective on thermal properties. Keywords: Lineer low density polyethylene, peroxide crosslinking, polyethylene, rheology Acknowledgement: This study has been financially supported by TUBITAK (Grant Number: 116M981).