High-quality, monodisperse, and size-controlled Ag–ZnS nanorods or nanowires have been synthesized successfully using Ag nanocrystals as seeds. Such one-dimensional colloidal Ag–ZnS nanorods or nanowires having a purposefully controlled diameter in the range of 5–9 nm and a length of 18–600 nm were obtained by altering the reaction conditions, such as concentration, reaction time, reaction temperature, and diameter of Ag nanocrystals. The conjunction interface of Ag–ZnS nanorods or nanowires consists of the (200) plane of Ag nanocrystal and (101) plane of ZnS rod or wire, the 〈101〉 directions of ZnS nanorods grow preferentially. Based on the photoluminescence and lifetime of Ag–ZnS nanorods, it was found that Ag nanocrystals enhanced the radiative rate eventually, the fluorescence intensity of Ag–ZnS nanorods can be tuned by changing the size of the Ag seeds. The Ag–ZnS nanorods or nanowires showed greatly improved optical properties as compared to ZnS nanocrystals, the maximum emission was around 402 nm and the photoluminescence quantum yield was up to 30% when 5 nm Ag nanocrystals were used as seeds.