Low-energy isomers of AgN clusters are studied within gradient-corrected density functional theory over the size range of N=9-20. The candidate conformations are drawn from an extensive structural database created in a recent exploration of CuN clusters [M. Yang, J. Chem. Phys. 124, 24308 (2006)]. Layered configurations dominate the list of the lowest-energy isomers of AgN for N<16. The most stable structures for N≥16 are compact with quasispherical shapes. The size-driven shape evolution is similar to that found earlier for NaN and CuN. The shape change has a pronounced effect on the cluster cohesive energies, ionization potentials, and polarizabilities. The properties computed for the most stable isomers of AgN are in good agreement with the available experimental data.