The announcement came two days after the former Crown Prince Nayef died Saturday in Geneva while receiving medical treatment for an undisclosed illness at age 78.
Saudi Arabia is one of the world's few remaining absolute monarchies, with members of the royal family holding all major governmental positions. Prince Salman will take on the late Prince Nayef's role as deputy prime minister while retaining his position as defense minister.
The line of succession in the Saudi monarchy transfers to the next eldest son of the late King Abdul-Aziz, who established the Kingdom of Saudi Arabia in 1932.
Prince Salman, 76, is viewed to be more progressive and secular than both his late brother and King Abdullah, 88.