Phase separation phenomena of PE/EVA binary blends were investigated in pure state and in the presence of unmodified nanoclay. Regardless of the composition dependency of interfacial interaction in pure blends, all the obtained samples showed upper critical solution temperature behavior in the molten state. Considering the results of rheology and the estimated interaction parameter, it can be found that the main origin of phase separation of these two polymers in the molten state would be entropic effect in nature. The addition of unmodified nanoclay to the blends with different compositions, however, influenced the viscoelastic properties of components and resulted in smaller disperse phase domains and finer morphologies except for PE-rich blend. Higher interfacial interaction of PE and EVA phases in the blends containing EVA dispersed domains reduced as the intercalated silicate layers located at the interface. Moreover, thermal analysis verified that these two components are immiscible in crystalline regions and solid-liquid phase separation phenomenon occurred while solidification was progressing. For all the prepared blends in the pure state, even imposing a restriction on liquid-liquid phase separation occurrence did not lead to their co-crystallization or their partial miscibility in the crystalline parts. In the presence of layered silicate, crystallization kinetics of PE and EVA phases was affected and both crystallization temperatures decreased to lower values. In addition, the solid surface of nanoclay did not act as nucleating agent for the both components. However, the simultaneous effects of nanoparticles and liquid-liquid phase separation restriction lead to higher degrees of crystallinity for the constituents. As the amount of dissolved chains of each phase in the other phase domains became noticeable in the prepared nanocomposites, the crystallization kinetics and the miscibility in the crystalline parts altered considerably.