Ranjbar began his coaching career as manager of Iran national under-20 football team in 1968. He was selected as assistant coach of the national football team in 1970 and was again selected as this position in 1971 by Parviz Dehdari. After Dehdari's resignation in 1972, Ranjbar was appointed as caretaker manager of the national team, which he led to the final victory in 1972 AFC Asian Cup. After the team's success with Ranjbar, Iran Football Federation appointed Ranjbar as the team's head coach and signed a two-year contract with him, but he resigned after two months.