A simple and scaleable method is proposed for suppressing internal porosity in various porous particles that are widely applied in packed-bed catalytic systems. The method is based on a complete filling of the pores by a cross-linked organic polymer. The particles were first loaded with the volume of organic monomer and cross-linker needed to achieve complete blockage of the porosity, and subsequently, in situ radical polymerization was performed with heating under reduced atmosphere. The method is shown to be adaptable for particles of various shapes, sizes, and porous structures. Selective and complete pore filling has been confirmed by nitrogen physisorption measurements, thermogravimetric analysis, and scanning electron microscopy. The different analyses confirm uniform pore blocking. The difference in contact angle before and after polymer impregnation was found to be negligible. The system is especially suitable for packed-bed hydrodynamic studies to disentangle extragranular hydrodynamic effects (such as axial dispersion) from intraparticle mass transfer effects, which are key to scaling down/up trickle-bed reactors. The liquid holdup and Peclet number for a trickle-bed reactor packed with polymer-impregnated spherical particles and glass beads, respectively, were compared for the compatibility of the method. For given superficial liquid and gas velocities corresponding to the pulsing flow regime, the external liquid holdup and Peclet number were found to be correspondingly close for both particles.