This paper explores flora of Rudbar Alamut region in NE of Ghazvin province situated in the south slope of central Alborz Chain Mountains. Alamut is divided into two parts, upper Alamut and lower Alamut. The minimum height in the region is 1265 m, located in Shahrak village, while the maximum height is 4175 m, located in Siahlan Mountain. Average of annual precipitation is 368.3 mm and annual average temperature is 14ºC. This reveals that 642 species and subspecies belong to 373 genera and 76 plant families growing in the region. The largest families are Asteraceae with 88 species, Paoilionaceae with 64, Poaceae with 56, Lamiaceae with 48, Brassicaceae with‌ 46, Apiaceae with 41, Charyophyllaceae with 34 and Rosaceae with 30, respectively. Nearly 190 species are medicinal plants, of which 51 are used traditionally by local inhabitatants, 59 species are endemic, 37 species are poisonous for animal and rarely for man, 75 species are weeds, 119 species are forage, and 17 species are cultivated.