The aim of this study is to investigate the effect of branching of LLDPE and POSS types on thermal, mechanical, rheological properties and shape memory behavior in crosslinked linear low density polyethylene (LLDPE)/POSS composites using different concentrations of peroxide. Shape memory polymers (SHPs) are intelligent materials that can recall their original shape from the temporary shape in which they are deformed, with an external stimulus that triggers the deformation. In this work, polyethylene (PE) copolymers of 1-octene (LLDPE-C8) and 1-hexene (LLDPE-C6) are utilized as the polyethylene types. Di-tert-butyl cumyl peroxide (BCUP) was used as peroxide (PRX) in 0.5, 1, 2 and 3 phr ratios. Octavinyl POSS (OvPOSS) and Octaisobutyl POSS (OibPOSS) were also added as potent co-agents. The composites were prepared in an Xplore micro-compounder. The crosslinking was carried out using a hot-press. The composites were characterized by performing tensile test, differential scanning calorimetry (DSC), rotational rheometer, FTIR and scanning electron microscopy (SEM). In rheometer analysis, OvPOSS was found to increase the complex viscosity, storage modulus, crosslink density, and found to decrease gelation times as peroxide amount increased, compared to OibPOSS. Plasticizing effect of OibPOSS was realized from rheology results. It was observed in shape memory tests that OibPOSS decreased shape recovery ratio whereas OvPOSS increased. When the polyethylene types were compared, the best shape memory results were obtained with LLDPE-C6.