<jats:p>By utilizing electrospinning technology followed by subsequent controlled carbonization processes, hierarchical porous three-dimensional carbon nanofiber mats (HPCNFMs) were successfully fabricated. Within the ternary blend, polyacrylonitrile served as the carbon source, while polyvinylpyrrolidone and polymethyl methacrylate were acted as pore-forming agents. Precise control over the pore size of the carbon fibers synthesized from the ternary blend system was achieved by leveraging differences in solubility. Among these, HPCNFM-3 displayed the most outstanding performance, combining robust mechanical strength and good hydrophobicity (water contact angle ≈ 141.4°) with a hierarchical pore structure. It achieved a high oil flux of 7723.80 L m−2 h−1, exceptional oil–water separation efficiency (&amp;gt;99.9%), and remarkable oil adsorption capacity (able to absorb 69–131 times its own weight). In addition, this material demonstrated superior flexibility. These superior performance attributes establish HPCNFM-3 as a highly promising material for advanced oil–water separation applications under diverse environmental conditions.</jats:p>