This work was aimed at understanding the influence of fibrillar morphology on melt viscoelastic properties of polymer blends containing various blend ratios (polypropylene/polytrimethylene terephthalate: 99/1, 94/6, 90/10, 80/20). The blends were processed on co-rotating twin-screw extruder, and fiber spinning was employed as a post-processing method. Scanning electron microscopy was used to analyze the interior morphology of the as-extruded samples and fibers, and it was revealed that droplet and fibrillar morphologies are the formed morphologies in as-extruded and fiber samples, respectively. To appraise the melt viscoelastic responses of samples, rheological measurements were conducted in both linear and nonlinear regions. Formed physical fibrillar network caused the storage modulus and complex viscosity to appear as a secondary plateau along with intensified values in low-frequency region compared with the as-extruded blend samples. Moreover, the fibrillar structure increased the elasticity of the fibers whose effect was monitored by increased values of transient stress responses and creep-recovery experiments.