In the title coordination polymer, {[Ag(C12H20N2O2)]ClO4·0.5H2O}n, the AgI cation is coordinated by two N atoms from two 1,2-bis(4,4-dimethyl-4,5-dihydro-1,3-oxazol-2-yl)ethane (L) ligands in a nearly linear geometry [N—Ag—N = 171.07 (8)°]. The L ligand bridges adjacent Ag+ cations, forming a polymeric chain running along the c axis. The lattice water molecule is situated on a twofold rotation axis, and links to the perchlorate anion via an O—H⋯O hydrogen bond. The long Ag⋯O separation of 3.200 (4) Å indicates a weak interaction between the perchlorate anion and the AgI cation. Weak C—H⋯O hydrogen bonding occurs between the chain and the lattice water molecule and between the chain and perchlorate anions. Both five-membered rings of the L ligand display envelope conformations; in one five-membered ring, the flap C atom is disordered on opposite sides of the ring with occupancies of 0.65 and 0.35.