We propose and demonstrate the application of high-pressure water-vapor annealing (HWA) to silicon photonic crystals for surface passivation. We find that the photoluminescence intensity from a sample treated with HWA is enhanced by a factor of similar to 6. We confirm that this enhancement originates from a reduction in the surface-recombination velocity (SRV) by a factor of similar to 0.4. The estimated SRV is as low as 2.1x10(3) cm/s at room temperature. These results indicate that HWA is a promising approach for efficient surface passivation in silicon photonic nanostructures. (C) 2010 American Institute of Physics. [doi:10.1063/1.3489419]