We have prepared the blends of poly(pentamethylene 2,6-naphthalate) (PPN) with poly(heptamethylene 2,6-naphthalate) (PHepN) by solution blending method and investigated their glass transition behaviour, melting behaviour, and tensile properties. It was observed that the blends of PPN/PHepN(9/1) and PPN/PHepN(1/9) have a single glass transition, reflecting a homogeneous phase, whereas those of PPN/PHepN(7/3), PPN/PHepN(5/5), and PPN/PHepN(3/7) exhibit double glass transitions, representing the existence of two phases. The PPN homopolymer annealed below $90^{circ}C$ shows triple melting peaks ($T_{m1}$, $T_{m2}$, and $T_{m3}$). It was proved that $T_{m1}$ is attributed to melting of thin lamellar formed during secondary crystallization process, $T_{m2}$ to melting of thick lamellar created during primary crystallization, and $T_{m3}$ to melting of crystals recrystallized after melting the primary crystals at $T_{m2}$. For the annealed PHepN homopolymer, double melting endotherms ($T_{m1}$ and $T_{m2}$) were observed, caused by dual lamellar population with different thickness, i.e. $T_{m1}$ corresponding to the melting of secondary crystal and $T_{m2}$ to primary one. The Hoffman-Weeks plots, applied to the melting of primary crystals ($T_{m2}s$), indicate that the equilibrium melting temperatures of PPN homopolymer, PPN/PHepN(9/1), and PPN/PHepN(7/3) blends are same to be $147^{circ}C$, and those of PHepN homopolymer, PPN/PHepN(1/9), and PPN/PHepN(3/7) blends to be $145^{circ}C$. Both the glass transition and melting behaviours demonstrate that the PPN/PHepN blend system is partially miscible. In addition, both the modulus and strength for the blends almost follow additive rule against blend composition, indicating that the PPN/PHepN blends are mechanically compatible over all blend compositions.