The reproduction biology of Caspian vimba, Vimba vimba (L.), was investigated on the southwestern coast of the Caspian Sea using 712 fish specimens collected at three fisheries catch stations located in Talesh, Anzali, and Kiashahr over a two-year period from April 2012 through June 2013. Seasonal changes in the gonadosomatic index, gonad histological status, size frequency distribution of oocytes, and the fecundity of the species were studied. The peaks of the gonadosomatic index (GSI) were observed both in females and males in June 2012 and May 2013 indicating the variable peak spawning time of this species. Histological examinations and oocyte frequency distribution patterns showed synchronous oocyte development in the Caspian vimba. Absolute fecundity ranged from 5873 to 35421 eggs. The size at first maturity for females was 120 mm FL. We concluded that the Caspian vimba is a total spawner with variable spawning dependent on environmental factors.