Selective separation of Tc-99 from aqueous process streams is of vital importance in view of its high fission yield, radioactivity, the long half-life, and high mobility in the environment. To this end, various processes have been suggested based on anion exchange resins, metal-organic frameworks, cationic polymer networks, polyprotonated azacryptands, etc. However, to date, very few of these materials have shown potential for application on commercial scales. We herein report a novel methyl triphenyl phosphonium nitrate (MTPN) polymeric resin; it is an easily scalable synthesis route and results in the selective separation of Tc over other radionuclides from aqueous streams. Fast sorption kinetics, high distribution ratio, and excellent selectivity for Tc over other radionuclides, along with the ease of back extraction, make this resin highly promising for the separation and recovery of Tc. Further, X-ray absorption spectroscopy (XAS), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS), and theoretical calculations were used to decipher the interactions responsible for the excellent uptake and high selectivity for Tc.