Mechanistic insights into bulk hydrogen-transfer polymerization of acrylamide initiated by t-BuONa are proposed in this study where attention is particularly given to the initiation and propagation steps. This anionic polymerization methodology led to the synthesis of polyamide-3 with controlled molar masses. NMR, SEC, and MALDI-ToF characterizations are supporting the chemical structures and the macromolecular dimensions of polyamide-3. The polymerization is completed in a few minutes depending on the targeted molar mass as confirmed by a complementary temperature vs time study. DSC and TGA measurements enabled the determination of the glass transition and degradation temperatures at 88 and 357 °C, respectively. Side reactions such as branching, transfer to monomer, and formation of polyacrylamide units were shown to occur and depend on the amount of base added. The formation of imide groups is also observed due to the formation of ammonia in the polymerization medium.