It is still challenging for synthesis of advanced nanomaterials and explores their electrocatalytic detection of hydrazine (N2H4) and bisphenol A (BPA). Herein, Pt-PtFe nanoparticles/three-dimensional (3D) porous N-doped carbon nanoflowers (Pt-PtFe/N-CNFs) were successfully prepared by high-temperature pyrolysis. The structures and properties of the nanocomposite were strictly investigated by various characterization techniques. The Pt-PtFe/N-CNFs displayed high-efficiency electrocatalytic activity for oxidation of N2H4 and BPA. Under the optimal conditions, the Pt-PtFe/N-CNFs based sensor exhibited the wide linear ranges: 0.5–559.5 μM and 559.5–2659.5 μM for detection of N2H4 with a limit of detection (LOD) of 0.19 μM (S/N = 3), coupled with a broad scope of 0.3–70 μM and a LOD of 0.043 μM for BPA. The developed sensor has promising applications in environmental and industrial samples.