Self-supporting zeolitic foams were synthesized by a geopolymer gel conversion process, employing silicon powder and hydrogen peroxide as foaming additives. The influence of silicon and hydrogen peroxide combination on the physical properties, mechanical characteristics, and pore distribution was studied. Correlations between these properties were drawn. This approach allows to manufacture porous monoliths tuned in terms of zeolite type and amount and characterized by bulk density ranging between 573 and 762 kg/m3 and thermal conductivity 0.33–0.53 W/mK. Pore structure, size, and distribution were dominated by the type of foaming agent: the foamed samples showed the presence of two classes of pores, the first of the order of magnitude of 1 μm, the second of the order of magnitude of 100 μm. The use of hydrogen peroxide enhanced the porosity in the meso-macropore range (0.1–5 μm). The hydrothermal treatment performed on the foamed geopolymer allowed to achieve the crystallization of zeolites within the solid geopolymer. Mainly FAU and LTA were the zeolitic phases present in the foams, whereas the use of silicon as foaming agent locally increased the Si/Al ratio on the geopolymer surface, promoting the nucleation of FAU.