Abstract Compatibilization is the modification of the interface in immiscible polymer blends in order to refine and stabilize their phase structure. The presence of a compatibilizer at the interface markedly affects the deformation behaviour of the dispersed droplets during and after cessation of flow. In this work the morphology development in blends of polystyrene and linear low-density polyethylene compatibilized with styrene-butadiene-styrene triblock copolymer during and after uniaxial elongation was investigated by means of electron microscopy and small-angle X-ray scattering. The incorporation of only 1 wt.-% of the compatibilizer led to a pronounced increase of the stationary elongational viscosity of the blend. It was found, that at moderate capillary number (Ca ≈ CaCR) the compatibilizer stabilises the droplets against break-ups during the flow. When Ca >> CaCR no differences in the deformation of uncompatibilized and compatibilized droplets were observed. After cessation of the flow, the presence of the compatibilizer prevented the droplet break-up and supported and accelerated the shape recovery of the elongated particles.