Systemic inflammatory response syndrome (SIRS) poses a serious threat that influences patient survival and life quality. Its early and accurate diagnosis is paramount in clinics, where procalcitonin (PCT) is recognized as a key serological biomarker. Herein, well-dispersed PtPdCo nanoalloy was efficiently anchored on hollow porous N-doped carbon fibers (termed PtPdCo HPCNFs) through a sequential process involving electrospinning, pyrolysis, etching, and co-reduction. The morphology, structure, and physicochemical properties of PtPdCo HPCNFs were characterized by a set of techniques. Subsequently, the synthesized PtPdCo HPCNF nanocomposite was applied to build a label-free electrochemical amperometric immunosensor for ultrasensitive detection of PCT. Its performance was evaluated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Notably, the biosensor demonstrated a wide dynamic linear range (0.0001–1000 ng mL−1) and a low detection limit (0.20 pg mL−1). Furthermore, the sensor achieved the bioassay of PCT in clinical samples, yielding acceptable results. This work offers a promising approach for synthesizing superior nanomaterials for bioanalytical applications, highlighting their potential in development of sensing devices, especially for early and sensitive diagnosis of SIRS through PCT detection.