The present contribution reports on the synthesis and controlled polymerization of a novel acrylamide monomer containing phosphonated moieties, namely diethyl-2-(acrylamido)ethylphosphonate. This monomer appears to be of great interest due to the phosphonated moieties, which can lead to a wide range of applications, associated with the chemical stability of the acrylamide compared to more common (meth)acrylate monomers. Reversible Addition–Fragmentation Transfer (RAFT) polymerization of this monomer was investigated using two different trithiocarbonate chain transfer agents, and it allowed the synthesis of poly(diethyl-2-(acrylamido)ethylphosphonate) with controlled molecular weight and low dispersity. Additionally, a diblock copolymer was successfully prepared by a similar RAFT procedure using thermosensitive poly(N-n-propylacrylamide) as a macro-chain transfer agent. A combination of both stimuli-responsive and phosphonated ester or phosphonic diacid (after hydrolysis) containing blocks appears valuable for drug delivery or water treatment, for instance.