This study reported a facile, one-step activation strategy for fabricating hierarchical, nitrogen- and sulfur-doped, porous, activated carbon (NSPAC) utilizing a NaOH/thiourea aqueous system. The morphology, amorphous nature, surface area, pore volume, and elemental composition of the NSPAC was characterized using SEM, HRTEM, EDS, XRD, Raman, BET, and XPS. The as-prepared, porous carbon exhibited a large specific surface area of 1800 m²·g⁻¹, a well-developed pore structure, and good nitrogen- and sulfur-doping of 3.29% and 0.32% respectively. The NSPAC was employed as sensitive material for constructing electrochemical sensors to determine dopamine (DA) and uric acid (UA). The glassy carbon electrode (GCE) modified with the NSPAC (NSPAC/GCE) shows excellent electrocatalytic activity and separation performance, with 135 mV of peak-to-peak separation for DA and UA. The linear response concentration of DA and UA ranges from 0.2 to 100.0 μM and from 0.2 to 50.0 μM respectively, and both have a detection limit of 0.1 μM. The analytical parameters of the sensor are excellent, and the activated carbon prepared using the alkali urea system shows considerable promise as an effective platform for monitoring trace dopamine and uric acid in biological samples.