Saffron (Crocus sativus L.) is one of the oldest medicinal and spice plants in the world. Several factors affect the growth and production of saffron including: age and the number of corms per surface area, soil texture, the time of plant culture, time and kind of irrigation, mineral nutrition and ecological factors. It seems that the quantity and quality of saffron products are greatly different at different plant ages. The plant or field age has important effect on growth indices of saffron and its secondary metabolites. In order to investigate the effects of plant age on secondary metabolites and some physiological factors of saffron, a research project was conducted in a completely randomized design with three replications at the research field of medicinal plants of the University of Zanjan. Three saffron farms with different biological ages of one, two and five years old were selected as experimental treatments, and then three plots were randomly selected from each farm and the desired traits were measured. Results showed that, increasing of the age of saffron plants in this experiment increased fresh weight of plant and dry weight of stigma. 5-yraes old plants showed the highest amounts of these traits. Whereas, the contents of soluble proteins and sugars and photosynthetic pigments were higher at first year and decreased by increasing of plant age. Number of secondary metabolites decreased when the age of plants increased as in one–year old saffron plants 26 metabolites and in 5-year old plants only 15 metabolites were detected. Loliolid (18%) and thymol (17%) in 1-year old plants and thymol (19%) and camphor (14%) in 5-year old plants showed the highest level among all detected secondary compounds. Generally according to these results, plant age has an important effect on the number and kinds of secondary metabolites in saffron which should be considered at the time of saffron harvesting.