The thermal and rheological properties of two types of metallocene-catalyzed linear low-density PEs (mLL-DPEs) and two LDPEs, as well as their blends, were studied using differential scanning calorimeter (DSC) measurements and rheometry. The DSC results showed that the mLLDPE-1 based on the hexene comonomer is immiscible with both LDPEs in crystalline states, whereas the mLLDPE-2 based on the octene comonomer is miscible with the LDPEs. This suggests that increasing the length of short chains in mLLDPEs can promote the miscibility of mLLDPE/ LDPE blends. The linear viscoelastic properties confirmed the immiscibility of the mLLDPE-1 with the LDPEs in the molten state, and the miscibility of mLLDPE-2 with LDPEs. In addition, the Palierne [1] emulsion model provided good predictions of the linear viscoelastic data for both miscible and immiscible PE blends. However, as expected, the low-frequency data showed a clear influence of the interfacial tension on the elastic modulus of the blends for the immiscible blends.