In this study, a facile and environmentally friendly method was used to prepare a freestanding supercapacitor electrode displaying excellent areal capacitance and good cycle life performance. First, we prepared polypyrrole nanoparticles (PPyNP) through a simple chemical polymerization using the plant-derived material curcumin as a bioavailable template. A PPyNP/-CNT freestanding composite electrode of high mass loading (ca. 14 mg cm) was prepared after blending the mixtures of the prepared PPyNP and functionalized CNTs (-CNTs). The performance of the as-prepared material as a supercapacitor electrode was evaluated in a three-electrode setup using aqueous 1 M HSO as the electrolyte. The PPyNP/-CNT freestanding composite electrode exhibited a high areal capacitance of 4585 mF cm and a corresponding volumetric capacitance of 176.35 F cm at a current density of 2 mA cm. A symmetric all-solid-state supercapacitor assembled using two identical pieces of PPyNP/-CNT composite electrodes exhibited maximum areal energy and power density of 129.24 μW h cm and 12.5 mW cm, respectively. Besides, this supercapacitor device exhibited good cycle life performance, with 79.03% capacitance retention after 10,000 charge/discharge cycles. These results suggest practical applications for these PPyNP/-CNT freestanding composite electrode-based symmetric all-solid-state supercapacitors.