AgBr nanowires within single-wall carbon nanotubes (SWCNTs) are extremely stable even under UV laser light illumination. The structure of AgBr nanowires within SWCNTs, which was confirmed by transmission electron microscopy, inhibits photoreduction to Ag by preventing the migration of Br atoms. Reduction of AgBr nanowires to Ag can be observed only when the outer SWCNT is structurally compromised by intense electron beam irradiation.